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REVISED EDITION. 



FIEST BOOK 



m 



CHEMISTET, 



FOR THE USE OF 



SCHOOLS AND FAMILIES. 



Br WORTHINGTON HOOKER, M.D., 

AUTHOR OF "child's BOOK OP NATURE," <' CHEMISTRY, " "NATURAL HISTORY," ETC. 






toiti) SllB0tration0. 



W^ 



NEW YORK: 

HARPER & BROTHERS, PUBLISHERS, 

FRANKLIN SQUAEE. 

1877. 




By Dr. WORTHINGTON HOOKER. 



THE CHILD'S BOOK OF NATURE. For the Use of Families and Schools; intended to 
aid Mothers and Teachers in training Children in the Observation of Nature. In three 
Parts. Illustrations. The Three Parts complete in one vol., Small 4to, Cloth, $1 60; 
Separately, Cloth, Part I., 60 cents ; Parts II. and III., 65 cents each. 

Paet I. PLANTS.— Part IL ANIMALS Pakt IIL AIR, WATER, HEAT, LIGHT, &o. 

FIRST BOOK IN CHEMISTRY. For the Use of Schools and Families. Revised Edition. 
Illustrations. Square 4to, Cloth, 65 cents. 

NATURAL HISTORY. For the Use of Schools and Families. Hlustrated hy nearly 300 
Engravings. 12mo, Cloth, $1 50. 

SCIENCE FOR THE SCHOOL AND FAMILY. 

Part I. NATURAL PHILOSOPHY. Hlustrated by nearly 300 Engravings. 12mo, 
Cloth, $1 50. 

Paet IL CHEMISTRY. Revised Edition. Illustrations. 12mo, Cloth, $1 50. 

Paet HL MINERALOGY AND GEOLOGY. Illustrations. 12mo, Cloth, $1 50. 



Publislied by HARPER & BROTHERS, Franklin Square, N. Y. 

' Either of the above volumes will te sent by mail, postage prepaid^ to any part of the United 
States or Canada, on receipt of the price. 



-^1\ 



Copyright, 1877, by Harper & Brothers. 



PREFACE. 



The idea of this book was suggested by a lady, wbo is a stranger to 
me, in a letter, a portion of wbicli I will quote bere. " I can not tell 
you bow mucb pleasure I bave bad in teacbing tbe Cbild's Book of 
Nature to my little daugbter. In giving my own opinion of tbat work 
I am also expressing tbe opinion of several otber motbers of my ac- 
quaintance, wbo agree witb me in pronouncing it tbe very best book of 
tbe kind wbicb we bave ever found. It is so plain and simple in its 
arrangement, tbat any cbild of common capacity can learn it witb ease 
and remember it well. Tbe subjects upon wbicb it treats are of a kind 
to interest all cbildren, and tbe pleasant way in wbicb you bring tbem 
forward is sure to awaken tbeir powers of observation and comparison, 
and, better still, to lead tbem * tbrougb Nature up to Nature's God.' It 
seems to me tbat an elementary book on cbemistry, upon tbe same 
plan, would be interesting to cbildren, especially if tbey could bave 
some simple and safe experiments wbicb tbey migbt try for tbem- 
selves." 

Soon after receiving tbis letter, I put tbe matter to a test in tbe fol- 
lowing manner: I selected a few of tbose scbool-rooms in tbe public 
scbools of New Haven in wbicb tbe scbolars were from eleven to tbir- 
teen years of age. I visited tbese rooms from time to time, talking to 



6 PREFACE. 

the pupils for half an hour on chemistry, without trying any experi- 
ments, but illustrating the subject largely from common every-day phe- 
nomena. At each visit I questioned them upon what I had told them 
at the previous visit, and allowed them to ask me questions. In this 
way I found out what they could understand, and what they wanted to 
know, about chemistry. I was surprised to see how much of this sci- 
ence was within the reach of their capacity, and, at the same time, could 
be made very interesting to them. During all this time I jotted down 
my results, and at length put them into the shape in which they now 
appear, so that the book was almost literally made in the school-room. 
I may add that nearly the whole has been subjected to the examination 
of one of the teachers whose rooms I visited, a lady to whom I am in- 
debted for many valuable suggestions. 

This book can be readily comprehended by pupils of average capaci- 
ty of twelve or even eleven years of age, especially if they have gone 
through with my Child's Book of Nature, which it is intended to fol- 
low. At the same time, it is fitted for older scholars to whom the 
subject of chemistry is entirely new. 

I need hardly say that there must be carefulness in experimenting, 
and that some of the experiments described in this book should be 
tried only by teachers, or by pupils under their supervision. 

This book is followed by three other books for the next higher 
grade of pupils. They are under one title — Science for the School and 
the Family. Part I., Natural Philosophy. Part II., Chemistry. Part 
in., Mineralogy and Geology. 

WORTHINGTON HOOKEB. 



PREFACE TO THE SECOND EDITION. 



In preparing a revised edition of this work no alteration has been 
made in its general plan ; a considerable diminution in size has been 
effected by general condensation, but it is believed that no leading fea- 
tures have been omitted. 

In adapting the nomenclature to modern theories and usage a com- 
promise has been attempted, and a change made which some may re- 
gard as not suflSciently radical ; but it has not seemed desirable to in- 
troduce the nice distinctions in terminology which are correlated to 
philosophical views, inasmuch as an explanation of these views is pre- 
cluded by the very elementary character of the work. 

The presentation of scientific truths to the youthful mind in a sim- 
ple and attractive manner was the peculiar faculty of the author, and 
the editor has endeavored to preserve this characteristic, and to avoid 
burying the subject beneath the exactions of a scientific nomenclature. 

H. Carrington Bolton, Ph.D. 

School op Mixes, Columbia College, 
New York J Septe^nhev^ 1876. 



CONTENTS. 



CHAPTER . PAGB 

I. THE CHEMIST 11 

n. OXYGEN 16 

III. NITROGEN 21 

rV. NITRIC ACID AND LACGHING-GAS 26 

T. CARBON 29 

TI. CARBONIC ACID 34 

VII. THE AIR WE BREATHE 40 

VIII. HYDROGEN. THE WATER WE DRINK 44 

IX. COMBUSTION . . 53 

X. GAS-MAKING AND GAS-BTJRNING 58 

XI. STRIKING FIRE 64 

XII. ANIMAL HEAT 68 

xni. moN-RUST, potash, and lime '73 

XIV. metals, iron 80 

XV. MORE ABOUT METALS AND THEIR COMPOUNDS 85 

XVI. SULPHUR AND PHOSPHORUS 92 

XVII. SALTS, SULPHATES, ETC 99 

XVni. LIMESTONE, SHELLS, AND CORALS 105 

XIX. PEARLASH AND OTHER CARBONATES Ill 

XX. GLASS AND EARTHENWARE 117 



10 CONTENTS. 

CHAPTER ' PAGB 

XXI. CHLORINE AND COMMON SALT 120 

XXII. IODINE AND SEA-WATER 127 

XXin. SOLUTION AND CRYSTALLIZATION 132 

XXrV. WOOD. PETROLEUM 140 

XXV. STARCH AND SUGAR 146 

XXVI. GLUTEN AND THE FOOD OF ANIMALS 152 

XXVII. FERMENTATION. VLNEGAR 157 

XXVIII. VEGETATION 161 

XXIX. HOW FOOD MAKES ANIMALS GROW 166 

XXX. CONCLUDING OBSERVATIONS 172 



THE FIRST BOOK H CHEMISTRY. 



CHAPTEE I. 

THE CHEMIST. 



What chemists do. Their discoveries. 

Ijst this book yon are to learn about chemistry. But what is 
chemistry? you will ask. This we will explain to you in part 
in this chapter ; but you can not understand fully what it is till 
you become well acquainted with what this science can show 
you. 

You see represented in the frontispiece a large room with a 
great many different kinds of vessels and instruments and appa- 
ratus. There are several persons, chemists, engaged in trying 
experiments. Their object is to find out of what things differ- 
ent substances are composed, and what effects will be produced 
when they are mixed. 

Chemists have discovered many things which will surprise 
you. You are in the habit of regarding each of the sub- 
stances that you see all about you as made up of one thing. 
The chalk with which you mark on the blackboard you think 
of as chalk, and that is all. But the chemist has discovered 
that chalk is made of three things put together. One of them 



12 



THE CHEMIST. 



Composition of water. 



Experiment. 



is a gas as tliin as air. In fact, it is a gas that forms a part of 
tlie air which, you breathe. Another is carbon, or charcoal. 
Yes, the charcoal makes a part of the white chalk ; bnt it is 
not black now, because it is united with other things. The 
third thing in chalk is a metal. A gas, charcoal, and a metal, 
then, three things very unlike each other, unite to form chalk. 

Then consider water, for example. "Water, simple water, that 
surely, you will say, must be one thing. People used to think 
so — old philosophers as well as common people and children. 
But chemists have found out that it is not so. Water is com- 
posed of the same gas as that in chalk, united with another gas 
sometimes used for filling balloons. These two gases are con- 
tinually uniting to form water all around you. This is going 



Fig. 1. 



on in every fire and every light that you see 
burning. In every fiame you see, whether it 
be flame of wood, or candle, or gas, or kero- 
sene, these two gases are busy uniting togeth- 
er to form water. You do not see the water, 
for as fast as it is formed it flies off into the 
air. It makes a part of the water in the air, 
which is so finely divided that you can not 
see it, as explained in Chapter XIX. of the 
Third Part of the Child's Book of Mature. 
But you can catch this water thus formed 
in the flame as it flies off, and make it to be 
seen. One way in which you can do this is 
represented in Fig. 1. Ice and salt are in the 
bowl, the object of which is merely to make the bowl very cold. 




THE CHEMIST. 13 



Catching water from flame. What it is to decompose. 

The bowl is held so far above the candle that the soot will not 
gather upon it. Now, the finely divided and heated water flies 
up, strikes against the cold bowl, and is condensed npon it. A 
large drop of water therefore hangs, as you see, from the bot- 
tom of the bowl, fairly caught and brought to view. 

You can do the same thing with a silver spoon or a glass gob- 
let, if it be cold. Held over a candle or lamp, moisture will 
gather upon it. You do not catch so much water in this way as 
with the bowl of ice and salt, because the surface is not so cold, 
and is smaller. 

Any thing which you try in a similar w^y is an experiment. 
Chemists are making experiments all the time, and by looking 
closely at the results they learn many new things. Experiments 
have proved that water is composed of two gases. Now, when 
the chemist takes some water and separates one of the gases in 
it from the other, we say that he deco7)vposes the water. He 
does just the opposite of what is done in flame, for there the 
two gases come together to form water. So, when he separates 
the ingredients of chalk from each other, he decomposes the 
chalk. 

We shall tell you, in other parts of this book, much more par- 
ticjilarly about these and a great many other wonderful things. 

Perhaps you have thought that you are too young to know 
any thing about chemistry, and that none but older and wiser 
persons can understand it. But this is not so. There are a 
great many things in chemistry that you can understand as well 
as the wisest man on earth. 

Chemistry will be interesting to you because it tells about so 



14 THE CHEMIST. 



Why you can understand Chemistry and be interested in it. 



many things that you see every day. You have very likely 
been in the habit of thinking that the chemist is engaged in 
finding out only about things which have hard names, and that 
you have nothing to do with. But it is far otherwise. Very 
many things that he can tell you about are the commonest of 
all things. We have already spoken of chalk and water. Then 
there is the air you breathe — you will like to know about that. 
The chemist can tell you what part of the air keeps you alive, 
and how it does it. You will be surprised to learn that some of 
the air is continually becoming a part of your body, your flesh 
and bones, and that some of your body is all the time turning 
into air and flying off all around you. But so it is, as we shall 
by-and-by show you. 

Chemistry will tell you how flres and lights burn. 

Chemistry will tell you what it is that makes bread rise, and 
how it is that the grain from which it is made is fitted in grow- 
ing to nourish your body. 

It will tell you how wine is made from grapes and other 
fruits, and explain what that is in the making of cider and beer 
which is called working. It will exjDlain, too, the making of 
vinegar. 

It will tell you how soaps are made, and explain the way in 
which they operate in cleansing clothes and freeing things from 
dirt. 

It will tell you about the making of different paints and dyes. 

It will tell you also how to find out if the things you eat and 
drink are pure, or whether substances are mixed with them 
which are not fit for food. 



I 



THE CHEMIST. 15 



Chemical experiments which you try every day. 



You liear a great deal about the experiments that the chem- 
ists try. In this book we shall tell you of many experiments 
that you can try for yourselves. You can try them with bottles 
and tubes that you can buy with a very little money, and many 
of them you can try by using a little ingenuity even with things 
that you can find about the house. 

But you will not need to do even this to be interested in 
chemistry, because there are things happening before you con- 
tinually that illustrate the subject. There are experiments, as 
we may say, going on all around you and even within you ; and 
you have only to look and to think, to get chemistry out of the 
commonest things. Every time that you rub a match, or set fire 
to gas, or hght a candle or a kerosene lamp, you make a chemical 
experiment. Every time you draw a breath, you make chem- 
ical work for your lungs. Every time you eat, you set in mo- 
tion in your stomach some of the chemical operations th^t the 
chemist in his laboratory or work-room makes in some of his 
queerly- shaped glass vessels. And your body is kept warm, 
as we shall show you in one of the chapters of this book, by 
a sort of chemical fire in you — a fire without a fiame. 

Questions. — What are chemists ? Of what is chalk composed ? Why is not the 
charcoal black in the chalk ? What did all people use to think about water ? What 
have the chemists found out about it ? Tell about the formation of water in flame. 
Why do you not see the water that is formed ? How can you catch the w^ater as it 
flies off ? What is decomposition ? Why can you expect to understand much about 
chemistry in studying this book ? Why will chemistry be interesting to you ? What 
things will chemistry show you about air ? What can the chemist tell you about 
bread ? What other things will chemistry explain to you ? What is said about ex- 
periments ? 



16 OXYGEN. 



Why words are hard. What you have to do with oxygen. 



CHAPTEE II. ■ 

OXYGEiq'. 

Oxygen, That is a hard word, yon will say. Why hard % 
Simply because it is new, and you do not understand what it 
means. When we have told you what oxygen is, and related to 
you the interesting facts about it, the word will be as easy to 
you as any other word of the same length of which you know 
the meaning. The names of many of your acquaintances would 
be hard words to you if they were not the names of those whom 
you know. JS'ow, we hope to make you as well acquainted with 
oxygen as you are with any of your friends, and then it will 
be quite as easy a name to you as Ellen, Henry, or Gertrude. 
Many words which you use every day are much longer than ox- 
ygen, such as amusement, dissatisfaction, experiment, etc. ; but 
they are easy to you, because you know what they mean. 

Though you are not yet acquainted with oxygen, you have a 
great deal to do with it. Indeed, you could not have done with- 
out it at any moment since you were born. Every time you 
draw a breath you take some of it into your lungs, for there is 
always oxygen in the air. If what there is in the air should 
be taken out of it, you would die as quickly as if you were un- 
der water. 

This oxygen is part of the food which nourishes your body. 
It does not, it is true, go into your stomach, but still it is just as 



OXYGEN. 17 



Oxygeu part of your food. Qualities of gases. 

necessary for your body as the food yoii swallow. It is food for 
your lungs, and yonr lungs must have it, or you will die. 

The food that you put into your stomach you can do without 
for some time. You can live without it even for days ; but the 
lung-food you must have every minute. 

The food that enters your lungs helps to make up the solid 
part of your bodies — your bones, muscles, skin, etc. But it is 
not sohd when it goes in. It is a gas. There are a great many 
different kinds of gases or airs. The air you breathe is a mix- 
ture of three of these gases. The gas we burn is very different 
from that we have in the air. If you live in a village, perhaps 
you never saw gas burning from a gas-burner. But you see a 
gas burning when you see a flame of sjry kind, whether it 
comes from wood, a candle, or a lamp. The oil or tallow is 
changed into gas before it burns. What we call flame is burn- 
ing gas. When wood or coal is burned, all except the ashes 
goes off into the air, and burns as it goes. 

Most gases have no color, and you can look through them as 
you look through glass. You are always looking through gases, 
for the air is a mixture of three gases. You can not see the air, 
and so you can not see any gas that has no color. For example, 
if a gas-burner be left open without being lighted, you can not 
see the gas coming out, although you can smell it. The color- 
less gases are said, then, to be transparent, like clear glass, be- 
cause objects are seen or apjpear through them, trans being a 
Latin word which means through. 

We shall tell you about many gases in this book, but first we 
must speak particularly of oxygen. 

B 



18 



OXYGEN. 



Oxygen the most abundant substance in the world. 



Oxygen, besides being a part of tbe air, forms a part of almost 
every thing you see. It forms a large part of all the water in 
the world. It is in your skin, and muscles, and bones, and ev- 
ery part of your bodies, and is an important part of the blood 
that runs in your veins and arteries. It is in all animals and all 
plants. It makes a part of the ground beneath your feet, and 
even the solid rocks are made in part of oxygen. This gas is 
the most abundant substance in the world. 

It may seem strange to you that so light and thin a substance 
as gas can make a part of any solid, as flesh or bone. But you 
see every winter a liquid become solid, for ice is solid water. 
Now, this same water, which is sometimes liquid and sometimes 
solid, is sometimes also as thin as air or gas. There is always 
some water in the air, even when it seems to be very dry ; and 
as in the clear air that seems so diy there is no water to be seen, 
the water must be as thin as the air itseK. It is no more strange 

that oxygen gas can be- 



Fig. 2. 




come a part of a solid, than 
that this water, as thin as 
gas, can be turned into 
solid ice. 

Oxygen gas can be sep- 
arated from some of the 
substances with which it 
is united, and so can be 
obtained by itself. The 
chemist commonly uses 
for this pm'pose a certain 



OXYGEN. 19 



How oxygen is obtained separate from other substances. 



powder. What this powder is we will not tell you now, but 
shall notice its composition in another book, W'hen you can un- 
derstand it better than at present. Titis powder is heated in a 
glass flask, by a gas lamp placed underneath, as represented in 
Fig. 2, on the opposite page. The oxygen, separated from the 
powder by the heat, passes over through the small tube, con- 
nected with the flask by a cork, and bubbles up from the end 
of the tube which dips under the water in the earthenware 
vessel. Over the end of the tube a glass vessel is placed, with 
its open end down. This jar is full of water at first, the water 
being kept in it by the pressure of the air on the surface of the 
water around it, as explained in the Child's Book of ]S"ature, 
Part III., Chapter IV. As the end of the glass tube is put 
under the mouth of the jar, the gas goes up in bubbles through 
the water, because it is lighter than water, and takes its place 
in the upper part of the jar. In this way the jar may be filled 
w^th the oxygen gas. When you want to use the gas for ex- 
periments you may remove the jar carefully, placing a piece 
of window -glass under the mouth of the jar to keep the gas 
from flying out. ^ ^ ^ ^.^ ^^ 

Many beautiful experiments can be tried with 
oxygen. 

Put a hghted candle into a jar of oxygen, as in 
Fig. 3. It will burn with a dazzling brightness, 
ajad will be rapidly consumed. The reason is this. 
It is the oxygen in the air that makes the candle 
bm^n at all. Of course, the more oxygen gets 
to the candle, the more brightly it will burn. 




20 



OXYGEN. 



Burning various substances in oxygen. 



Fisr. 4. 




In the same way, a piece of charcoal, or of sulphur lighted 
and plunged into a jar of oxygen, burns much more brightly 
than in th» air, but no substance burns in oxygen 
with so brilliant a light as phosphorus, Fig. 4. A 
very thick white smoke arises, which is most brill- 
iantly illuminated. 

Some substances, which most people think can 
not burn at all, burn very readily in oxygen. Iron 
is one of these. If you take a piece of steel wire, 
and twist it as shown in Fig. 5, you can make a splendid fire 
with it in the oxygen. But how wiU you manage it ? 
You can not set it on fire in the air, and then introduce 
it into the oxygen, as is done with the phosphorus, on 
the candle. It is managed in this way. The end of it 
is dipped in sulphur, or has a bit of something which 
will burn in common air fastened to it, as cotton or 
charcoal. You light this substance, and then introduce 
the wire into the jar of oxygen. The substance on the end of 
the wire, in burning, sets fire to the wire itself, and then the 
sparks fly very prettily. 



Mg. 5. 




Questions. — What is said about the word oxygen ? What would happen to you if 
you could not get any of it into your lungs ? What is said about oxygen as food ? 
What does oxygen gas help to make in your body ? Of what is the flame in a candle 
or lamp made ? What is said about gases being transparent ? Mention some of the 
things in which there is oxygen. What is said about its making a part of solid sx^- 
stances? Tell about obtaining oxygen gas. Describe and explain the experiment 
with a lighted candle. How does phosphorus burn in oxygen ? Describe the way in 
which a steel wire blirns in oxygen. 



NITEOGEN. 



21 



How nitrogen differs from oxygen. 



Why nothing can burn in nitrogen. 



CHAPTEE III, 



NITEOGEN. 

To every gallon of oxygen in the air there are about four gal- 
lons of another gas called nitrogen. 

This gas is very different, in some respects, from oxygen. 
Nothing will bnrn in it. If yon put a lighted candle into a 
jar of oxygen, it will, yon 
know, burn more brightly 
than it does in the air. 
But if you take it out of 
the -oxygen, and" put it into ' 
a jar of nitrogen, it will go 
out. Not even phosphorus 
will burn in nitrogen. So, 
if all the oxygen should be 
taken out of the air, every fire and light would be extinguished. 

Besides this, no animal can live in nitrogen gas. If you put a 
bird into a jar of oxygen, it will be more lively than in common 
air, and will act as if crazy, jumping about in the most singular 
manner ; but if you should put it into a jar of nitrogen, it would 
die at once. And if all the oxygen should be taken out of the 
air, all animals would die, just as all the fires and lights would 
be extinguished. 




22 NITEOGEN". 



Why animals can not live in nitrogen. What would happen if the air were all oxygen. 

But this nitrogen gas does not really pnt out fires and lights. 
A light, when placed in a jar of nitrogen, goes out merely be- 
cause there is no oxygen. If you mix a little oxygen with the 
nitrogen, the candle will burn, just the same as in common air, 
which is really a mixture of oxygen and nitrogen. 

So, too, nitrogen does not kill any animal, although he can 
not live in it. It does not act as a poison when it goes into the 
lungs; for four times as much nitrogen as oxygen enters the 
lungs of animals, all the time. The bird dies in the jar of 
nitrogen simply because nitrogen can not keep it alive. 

Of what use, then, is the nitrogen in the air, as it does not 
help to make any thing burn, or keep any thing ahve ? "We 
will tell you. 

Suppose the air were all oxygen, instead of being a mixture 
of oxygen and nitrogen. "What would happen ? You can see 
by calling to mind the experiments in which different things 
were burned in jars of oxygen. Our fires and lights would 
burn very brightly. This would sometimes be quite conven- 
ient. We should not be troubled with dull fires and dim lip:hts. 
It would be one of the easiest things in the world to kindle a 
fire. But then, on the other hand, there would be a great deal 
of inconvenience and danger from so much oxygen. Things 
would burn too fast. We should have thing's takino^ fire much 
oftener than now; and when a fire once started it would be 
very hard to put it out. If a block of houses should take fire 
at one end, the whole block would be burned. Whole towns 
and cities would often be destroyed. 

Besides all this, if the air were wholly oxygen it would be 



NITROGEN. 23 



Why there is so much nitrogen in the air. 



injurious to animals. It would be too heating, too stimulating. 
With so much oxygen going into our lungs, we should be all the 
time as warm as we are after exercising violently. This would 
make us very uncomfortable. We should be forever fanning 
ourselves, and drinking cold water, and seeking for cold air. 
Inflammations and fevers would be produced, and we could not 
live long in this way. 

It is chiefly for these reasons that God has given us our oxy- 
gen mingled with so much nitrogen. It is very much as we 
take some medicines. They are put into sugared water because 
it would not be agreeable for us to take them clear. The sug- 
ared water is to the medicine as the nitrogen is to the oxygen. 
Suppose the medicine is some strong acid. It would make your 
mouth sore if you should take it clear, so we dilute it, as we say, 
with sugared water. In like manner, the oxygen is diluted with 
nitrogen, that we may take it into our lungs without harm. 

Nitrogen, you see, is a very mild gas when free, as it occurs 
in the air. But when it combines in a chemical way with oxy- 
gen, it forms very dangerous gases, quite unhke the air. Nitro- 
gen also forms a part of all animals, as well as some parts of 
vegetables. It is also one of the two ingredients of ammonia, 
or hartshorn, which tingles your nose whenever you smell it. 

Ton can get nitrogen gas from the air by a very pretty experi- 
ment. All you need is a basin of water, a glass jar, a fiat cork 
smaller than the mouth of the jar, and a bit of phosphorus. 
Hollow out a little place on the cork and float it on the basin of 
water. Then with pincers pick up a piece of phosphorus about 
the size of a pea, and place it on the cork. If you touch the 



24 



NITROGEN. 



How to obtain nitrogen gas from the air. 



Fig. 7. 



phosphorus with your fingers, yon may burn them badly. ISTow 

set fire to the phosphorus as it 
fioats on the cork, and put the 
jar over it with its edge in the 
water. Think, now, what you 
have in the jar. There is a 
mixture of oxygen and nitro- 
gen, that is, air. Then you have 
the burning phosphorus. ITow, 
oxygen is there. If there were 
nothing but nitrogen in the jar, 
it would not burn at all. If you watch the experiment, you will 
see that, after a little while, the phosphorus burns rather dimly, 
and at length goes out, although there may be considerable phos- 
phorus left. This is because the oxygen is all gone, and there 
is nothing now but nitrogen in the jar. 

You will see that the cork has risen in the jar, being pressed 
up by the water. "Why ? The part of the air in the jar which 
is oxygen is used up, and so makes room in the jar, and the 
water and cork are pressed up to fill this room. One-fifth of 




the air in the jar is gone, for oxygen forms one -fifth of the 



air. 



But what has become of the oxygen ? It is not lost in the 
burning. It is united with the phosphorus,, and they, together, 
make the white smoke which arises when phosphorus is burned. 

This smoke soon disappears, for it dissolves in the water, 
forming with it an acid called phosphoric acid. Thus the ni- 



NITROGEN. 25 



Explanation of the preceding experiment. 



trogen is left alone in the j^r. In this experiment the nitrogen 
is not changed* The burning phosphorus does not unite with 
it, but takes all the oxygen out of its company. The phosphorus 
has a strong affinity, as chemists say, for oxygen, while it has 
none for nitrogen. 

Questions. — What proportion of air is nitrogen ? Tell about putting a lighted can- 
dle in this gas. What would happen to the fires and lights if all the oxygen were 
taken out of the air ? Why does a light go out when put into nitrogen gas ? Why 
does an animal die when put into it ? Tell what would happen to fires and lights if 
the air were all oxygen. What influence would it have on animals ? Of what use is 
the nitrogen in the air ? What does the word dilute mean ? What is said about the 
character of nitrogen ? How would you arrange your apparatus for obtaining nitro- 
gen ? Why does the phosphorus burn ? Why does the cork rise in the jar ? What 
becomes of the oxygen in the jar ? How is it that the nitrogen is left alone in the 
jar ? Is the nitrogen changed by the phosphorus in this experiment ? 



26 NITKIC ACID AND LAUGHmG-GAS. 

Nitric acid a compound. How lightning makes it in the air. 



CHAPTEE IV. 

KITEIC ACID AND LAUGHING-GAS. 

In air, as you have seen, oxygen and nitrogen are only mixed . 
together. The oxygen is diffused through the nitrogen as alco- 
hol is diffused through water when they are mixed. But oxy- 
gen and nitrogen can combine in such a way as to form com- 
pounds that are very different from the mixture we call air. 

One of these compounds united with water forms a very 
powerful acid called nitric acid. It will destroy cloth, and even 
flesh, if dropped upon it. How strange it is that such a biting 
acid is composed of water and two gases that are so quietly go- 
ing into our lungs every time we breathe ! 

These gases, mixed so thoroughly in the air, have no dispo- 
sition to unite together to form this acid. It is very difficult 
to make them unite. All the shaking which the air gets in 
violent winds and whirlwinds will not do it. Air is sometimes 
greatly heated, but the heat of the hottest furnace can not unite 
the oxygen and the nitrogen of the air. A flash of lightning, 
as it passes along through the air, will make them unite so as to 
form nitric acid ; but only a little is made in this way. This 
little, however, being carried down in the rain, is of use to the 
farmer and the gardener in making things grow. 

There is another compound of these two gases which is of a 



NITEIC ACID AXD LAUGIIIXG-GAS. 27 

Singular effects of laughing-gas. How it differs from nitric acid. 

very different character from the nitric acid. It is in the form 
of a gas. It can be breathed, and it does not irritate the hmgs. 
It produces, however, a very singular effect upon the system, 
greatly exciting the person who breathes it. Under its influ- 
ence different persons act very differently. One, perhaps, bows 
and smiles continually ; another dances ; another laughs ; anoth- 
er declaims with great eloquence ; another wants to fight — and 
so on. The dehrium lasts but a few minutes; and when the 
person recovers, he does so all at once, and seems to be haK 
ashamed of what he has been doing. 

Xow, a person in breathing this gas takes iiito his lungs oxy- 
gen and nitrogen, as he does when breathing aii' ; but they are 
not merely mixed, as in air, but form a compound, a new 
thing, different from both the oxygen and nitrogen. Neither 
nitrogen nor oxygen-, nor their mixture in air, ever produces an 
intoxicating effect, as does their compound, laughing-gas. 

Laughing-gas does not occur ready formed in nature; it ig 
only made in the chemist's laboratory, by heating a certain white 
crystalline substance in a glass vessel, somewhat in the same way 
that oxygen is prepared. Before the gas is given to persons to 
breathe, it must be carefully purified by j)assing it through a 
solution of potash, and in other ways. 

Observe how these two compounds, nitric acid and laughing- 
gas, differ from each other. One is a liquid which stains and 
corrodes. The other is a gas, soft and mild, but when breathed 
it makes people delirious. It so often makes them laugh, that 
this has given it its name. 

The reason of the difference between the two lies in the dif- 



28 NITEIC ACID AND LAUGHING-GAS. 

What would happen if oxygen and nitrogen united easily. 

ferent proportions of the ingredients. The nitric acid has a 
great deal more of oxygen in it than the langhing-gas. 

Suppose that the oxygen and nitrogen in the air were very 
mnch disposed to unite to form compounds. What would hap- 
pen ? Suppose, for example, that once in a while these gases 
should unite in the air and make a large quantity of laughing- 
gas. In whatever country this should happen, all the people 
— ^men, women, and children — would be running about crazy, 
laughing, fighting, and playing all manner of strange pranks. 

Or suppose that these gases should all at once unite to form 
nitric acid in the air. It would rain down upon the people, de- 
stroying the life of every animal and every plant, thus making 
the earth desolate. 

But the Creator has so made these gases that they can not 
unite when they are mixed, and the air is one of the mildest 
and pleasantest of all the mixtures that he has given us. When, 
at the end of the creation, he pronounced all his works to be 
"very good," he meant the air as well as other things. It is 
good — very good — for all the purj)oses for which it is wanted. 

Questions. — Is air a compound ? Of what is nitric acid composed ? What is said 
of the difference between this and the gases that compose it ? What of the difficul- 
ty of making these gases unite to form nitric acid ? Tell about the effect of light- 
ning upon them. Of what is laughing-gas composed ? What are its effects when 
breathed ? What is said of its being a compound ? What of the difference between 
this compound and nitric acid ? What is the cause of this difference ? If the oxy- 
gen and nitrogen in the air were very ready to unite together, what effects would be 
produced ? What is said about the creation of air ? 



CAEBON. 



29 



CiirboDic acid in the air. 



Difference between elements and compounds. 



CHAPTEE Y. 




CAKBOX. 

Thus far we have spoken of there being two gases in the mix- 
ture we call air. But there is a third gas, in ver j small quantity, 
in the air, called carbonic acid, or car- rig. s. 

bonic acid gas."^ There is only one gal- 
lon of this gas in every 2500 gallons of 
air. The proportions of the three gases 
in the air may be illustrated by Fig. 8. 
The largest square represents the nitro- 
gen ; the next, the oxygen ; and the 
very little one, the carbonic acid. Although there is so small 
•a proportion of this gas in the air, it has a very important in- 
fluence. 

Carbonic acid gas differs from oxygen and nitrogen in being 
composed of two things. Neither oxygen nor nitrogen can in 
any way be divided. They are therefore called elements^ or ele- 
mentary substances. But carbonic acid is not an element, but 
a compound^ for it is made of two things tinited in one. Ob- 
serve that these two things are not mixed^ as the two elements 
nitrogen and oxygen are, in the air; but they are united so 

* This gas is also called carbonic anhydride, for reasons given in Science for the 
School and Family, Part II., second edition. In this book, we will call it simply 
carbonic acid. 



30 CAEBON. 



CharcoaL Coal. Black-lead. Diamonds. 

as to make one thing in effect — as mucli one as if it were really 
an element. The two elements which compose carbonic acid 
are your lively friend oxygen, which yon have become so well 
acquainted with, and another that we will now introduce to your 
acquaintance, carbon. 

Carbon appears in various forms, bat the most common is that 
of charcoal. It is for this reason that the two names,- charcoal 
and carbon, are ordinarily used by chemists as meaning the same 
thing. The various kinds of coal we burn are chiefly carbon. 
Graphite, or black-lead, as it is called, is a form of carbon. It is 
this which is used in our lead-pencils. The name black-lead is 
very improper, for there is not a particle of lead in this sub- 
stance. It is wholly carbon, with the exception of a very little 
iron which is generally present. 

In the diamond we have carbon perfectly pure and beautifully 
crystallized. How strange that this most costly and brilliant of 
gems should be made of the same material with common dull 
and black charcoal ! But so it is. And yet no man has ever 
discovered any way of changing charcoal into diamonds. The 
Creator alone knows how diamonds are made. 

Diamonds are very expensive. Fifty dollars will buy but a 
small one. The largest one ever foimd is about the size of haK 
a hen's egg. The famous one which now belongs to the Queen 
of England is less than half of the size of this, but it is valued 
at three millions of dollars. 

Diamonds are found in the sands of rivers in Brazil, in Afri- 
ca, and rarely in the United States. 

The diamond is the hardest substance in the world. You can 



CARBON. 



Burning of diamonds. How charcoal is made. 

not scratch a diamond with any thing but another diamond ; 
and in preparing a diamond for use as an ornament, it is ground 
with the powder of diamonds. The instrument with which the 
glazier cuts glass has a small diamond in its end. 

All the different forms of carbon can be burned. Most of 
them burn in common air ; but black-lead and the diamond will 
not. To burn them, you must have oxygen alone, without any 
nitrogen. 

When carbon burns, it unites with oxygen, forming carbonic 
acid gas ; this same gas results whether we use carbon in the 
shape of diamond, graphite, or charcoal. 

It is rather an expensive experiment to burn up a diamond, 
and it is not often performed. 

The charcoal we use is, you know, made from wood. It is 
wood partly burned. It is made by burning wood in a heap, 
covered up with turf and dirt. Small openings are left above 
and below, so that a little air can circulate among the wood, 
and thus keep up a smothered burning. 

Wood is composed of carbon united with some other things ; 
and when wood is burned just enough to drive out these other 
things, the carbon remains. If too much air gets to the wood, 
the carbon itseK will burn too, and, uniting with the oxygen, 
will fly off in the form of carbonic acid gas. Wood, even though 
it may seem to be dry, contains considerable water, and this is 
driven off by the heat. 

You can readily make charcoal in a small way. Take a test 
tube (Fig. 9, on the following page), and hold a burning slip of 
wood in it. The tube prevents the air from getting freely to 



32 



CAEBON. 



How hard coal was made. 



How lamp-black is made. 




^^s- ^' the wood, and makes a smothered bm^n- 

ing, and so yon have a slender piece of 
charcoal. 

Hard coal is almost wholly carbon. It 
differs from charcoal in being very solid. 
It is supposed that all the coal that man 
gets ont of coal-mines was once wood. 
How, then, did it become coal ? Man can 
not make snch coal from wood ; but God 
can do a great many things that man can 
not do. But do we know how the Creator 
made this hard coal ? We know something abont it. We know 
that there mnst have been great heat and great pressure at the 
same time. While the wood was heated or partly burned, the 
rocks and earth above it were pressing down upon it, and so 
made the coal very solid. 

Soot is mostly carbon. It is made up of little particles of 
carbon, which are thrown off from the burning wood, and lodge 
on the chimney's sides. 

When a lamp smokes because the wick is too high, the smoke 
is made up of these little particles of carbon, for oil, as well as 
wood, contains carbon. It smokes because more oil rises in the 
wick than can unite with the oxygen supplied. If you could 
make the oxygen come to the wick faster, it would stop the 
smoking ; for then there would be oxygen enough to turn all 
the carbon into carbonic acid gas. 

The lamp-black much used in painting is a kind of charcoal. 
It is made by letting the smoke of burning pitch or rosin into a 



CARBON. 33 



Carbon very abundant, and in many different substances. 



sort of chamber lined with leather, on the sides of which it col- 
lects. 

There is much carbon in many very different things : it is in 
chalk and marble. It is combined in these with oxygen and 
lime ; so that it does not show itself as carbon any more than in 
carbonic acid gas. It is in egg-shells, oyster - shells, and in all 
kinds of shells. It is in all wood, and makes an important part 
of all leaves, flowers, and fruit. Your body, and the bodies of 
all other animals, have carbon as one of their principal ingre- 
dients. But it does not show itself in them as carbon any more 
than in the white chalk and marble. It is hidden in them by 
being united with other things. By separating it from these 
things, it can be brought out from its concealment, and shown 
to be carbon, as is done when charcoal is made from wood. 

Questions. — How many gases are there in the air ? How much carbonic acid gas 
is there in it ? WTiat is an element ? What elements are there in the air ? Why 
is carbonic acid called a compound ? What is the most common form of carbon ? 
W^hat is graphite ? What is the diamond ? What is said of diamonds ? What is 
said of burning carbon ? What is formed when we bum it ? How is charcoal com- 
monly made ? What becomes of the water that is in the wood ? How does hard 
coal differ from charcoal ? How is it probable that it was made ? Tell about soot. 
Why does a lamp smoke when the wick is high ? What is lamp-black, and how is it 
made ? Mention some of the substances that have carbon in them. 

c 



34: CAEBONIC ACID. 



How carbonic acid is obtained from chalk and marble. 



CHAPTEE YI. 

CAEBOXIC ACID. 

Caebois'ic acid gas, as yon learned in the previons chapter, is 
composed of the solid carbon and the gas oxygen. The solid is 
no longer a solid, bnt is united with a gas to form another gas ; 
and then this gas thus formed unites with many substances to 
form solids. In marble, for example, this gas is combined with 
lime. Kow, we can obtain carbonic acid gas from the marble 
by putting with it something which will take the lime away 
from it, and this is done by strong acids. There is an acid 
called hydrochloric, very corrosive, and sometimes fuming in the 
air; if you pour some of this, mixed with water, into a bottle, 
and throw in pieces of marble, gas will bubble up through the 
water, effervescing, as it is called, like soda-water. In a short 
time the bottle will fill with the gas, though you can not see it. 
To find out if the bottle is full, light a splinter of wood, and dip 
it into the apparently empty bottle. The gas extinguishes the 
flame, nor will a candle burn in the gas ; so you see things will 
not burn in carbonic acid gas. Why does the candle go out in 
this gas ? Because there is no oxygen there to make it burn. 

As nothing can burn in this gas, so no animal can live in it. 
Put a mouse into a jar of it, and he will die at once. There is 
a little of this gas in common air, but so very little, that it does 
no harm to us or to other animals. 



CARBONIC ACID. 



OO 



Experiments with carbonic acid. 



Its weight. 



Carbonic acid gas is much heavier than air. 
Yon can therefore ponr it, like water, from 
one vessel into another. 

If you place a lighted candle in a jar of 
common air, and pour into the jar some of 
this heavy gas (as shown in Fig. 10), the gas 
will go down into the lower jar, forcing out 
the air and putting out the light. 

Carbonic acid gas is heavy enough to be 
weighed. Perhaps you think it is not possi- 
ble to weigh something which you can not 
see, but it may be done with the apparatus 



Fig. 11. 



Fig. 10. 





shown in Fig. 11. 
Balance a jar of 
air on the scales, 
and then pour 
into the jar some 
of the gas ; the 
jar will then fall, 
and the weight 
will rise. This 
shows that the 
gas is much heav- 
ier than the air. 

As carbonic acid 
gas is so heavy, it 
is apt to remain 
below air wherev- 
er it collects. It 



36 



CAEBONIC ACID. 



Danger of carbonic acid in wells. 



The remedy. 



sometimes collects in considerable quantity in wells. When 
this is the case, it remains at the bottom of the well. Suppose 
a man goes down into snch a well to clean it : he will have no 
diflficulty at first, because the air is good — that is, it has enough 
oxygen in it, and not too much carbonic acid ; but when he 
gets near the bottom, where the carbonic acid gas has accu- 
mulated, he gasps for breath, and falls. Perhaps some one, not 
understanding the cause of the trouble, goes down to relieve the 
man, and he also falls senseless. Many lives have been lost in 
this way. 

ITow, how can we find out whether this gas has collected in a 
well ? Let a light down. If it goes out, there is a good deal of 

the gas there ; and if it burns 



Fis:. 12. 




dimly when it comes near the 
bottom, there is enough of the 
gas to make it dangerous. A 
very good way is for the man 
who goes down a well to take 
a candle with him, as you see 
in Fig. 12. He must hold the 
candle considerably below his 
mouth, or it will do no good. 
If his light goes out, or be- 
comes quite dim, he must stop 
at once, for another step would 
bring his head down into the 
gas, so that he would take it 
into his lungs. 



CAEBONIC ACID. 37 



Why the carbonic acid gas mixes with the air. The Grotto del Cane. 

To get rid of the gas, you can let down a bucket into the 
well, and raising it to the surface, turn it upside down, to let the 
gas out. This must be done a great many times. If this plan 
does not remove the gas, a bundle of burning straw may be let 
down into the well. This will heat the gas and make it rise, 
while good air will take its place. 

You have already learned that there is some carbonic acid 
gas in the air, mixed with the oxygen and nitrogen. Why is it 
thus mixed with them ? As it is heavier than these gases, why 
does it not lie all along close to the earth, with these above it, 
as water lies under the lighter oil when they are in a vessel to- 
gether ? It is because gases are so ready to mingle together. 
The least motion will make them do it at once, and you know 
that there is always motion in the air, even when it appears to 
be still. 

But at the bottom of a well or a pit, where the air is not in 
motion, the gas collects there quietly, just as it did in the bot- 
tle when we poured hydrochloric acid on marble. 

There are some places on the earth where carbonic acid col- 
lects in large quantities. There is such a place in Italy, called 
the Grotto del Cane, or Dog's Grotto. The reason of this name 
you will soon see. On the floor of this grotto or cave there is 
always a layer of this gas. The layer is high enough to reach 
above the head of a dog, but not the head of a man. A man 
lives near by who shows the grotto to visitors, and when he 
enters he takes his dog in, who, of course, falls down senseless. 
He brings him out, however, quickly into the fresh air, which, 
with a dash of cold water, revives the dog, so that the same 



38 CAEBONIC ACID. 



Carbonic acid in beer, cider, and soda-water. 



thing can be shown to the next visitors. Eather crnel sport ; 
but visitors to the cave almost always want to see the experi- 
ment. The gas in the grotto comes out of the crevices in the 
rocks^ and it collects on the floor of the cave, because the air is 
so shut in that the wind can not reach it. 

When wood or charcoal burns, this same carbonic acid gas is 
formed ; if charcoal is burned in an open furnace, in a close 
room, with all the doors and windows shut, the gas collects and 
makes the air very bad to breathe, sometimes poisoning persons. 
The remedy is very simple : you should open the doors and 
windows, to let fresh air in and the poisonous gas out. 

There is considerable carbonic acid gas in beer, champagne, 
bottled cider, etc. * It is that which bubbles up and makes the 
foam when the cork is drawn. "Where is it before we draw the 
cork ? If you hold the bottle up to the light, you see nothing 
there but the liquid. But the gas is all there. Its particles are 
all crowded in and concealed among the particles of the liquid. 
The gas is imprisoned, as we may say. But when we draw the 
cork, it is set at liberty, and, as it comes out eagerly and quick- 
ly to the air, it carries up some of the liquid with it, making a 
froth. In what is commonly called soda-water there is no soda, 
but it is water into which carbonic acid gas has been forced by 
machinery. 

We sometimes, however, make soda-water with two white 
powders: we dissolve one in some water in one tumbler, and 
the other in water in another; pouring them together, the gas 
bubbles up and makes a froth. One of the white powders is a 
carbonate of soda — that is, soda and carbonic acid; the other 



CARBONIC ACID. 39 



How soda powders act. Healthf ulness of carbonic acid gas. 

powder is tartaric acid ; and when the two are mixed, the tar- 
taric acid drives out the carbonic acid, which goes off as a gas. 

When we drink soda-water we take some of this gas into onr 
stomach ; but although the gas is poisonous to our lungs, it not 
only does no harm in the stomach, but is refreshing, and does 
us good. 

Questions. — What is said of the formation of carbonic acid gas ? What is marble 
made of ? How can the carbonic acid be separated from the marble ? Will things 
burn in this gas ? Why not ? Can animals live in it ? Show how we prove that the 
gas is heavier than air. Explain what sometimes kills persons in a well. How can 
the gas in the well be got rid of ? What is said of gases mingling ? What happens 
in the Dog's Grotto ? What is said of close rooms ? How do you explain the froth- 
ing of beer and soda-water? Explain the making of soda-water with two powders. 
Is carbonic acid healthy to breathe and to drink ? 



40 THE AIR WE BKEATHE. 

Quantity of carbonic acid in the air. How the air is affected by fires and lights. 



CHAPTEK YII. 

THE AIR WE BREATHE. 

You have already learned that the air is a mixture of about 
four parts of nitrogen gas with one part of oxygen and a small 
amount of carbonic acid gas. JSTow, although there is such a 
very small proportion of the carbonic acid, as shown in the fig- 
ure on page 29, yet there is really a great quantity of this gas 
in the whole of the air, for you must remember that the atmos- 
phere is 45 or 50 miles high. It is calculated that over every 
acre of land there are seven tons of carbonic acid gas. 

There are continual additions made to the carbonic acid in 
the air in various ways. Every fire or light that burns adds to 
it; for the burning of carbon in wood and other substances 
unites with the oxygen of the air, and forms carbonic acid gas, 
which flies off. 

Fires and lights lessen the oxygen of the air at the same time 
that they add to the carbonic acid. If you put a candle under 
a glass jar with its open end downward, it wiU burn brightly at 
first, because there is enough oxygen in the air inclosed in the 
jar ; but soon it will burn dimly, and, after a while, go out. The 
reason is that the carbon of the candle uses up the oxygen by 
uniting with it to form carbonic acid. If, just as the candle is 
about to go out, you lift up the jar, the flame of the candle will 
brighten up again, because you let out some of the carbonic 



THE AIK WE BREATHE. 41 

Making chalk with the breath. Quantity of charcoal in the breath. 

acid, and the fresh air that comes in supplies the candle with 
oxygen. 

Then, too, every animal is breathing out carbonic acid from 
its lungs. This you can prove in your own case by a simple ex- 
periment. Put some lime into a bottle, fill the bottle with wa- 
ter, shake the contents, and let stand until well settled. Pour 
off the clear water, which now contains lime in solution, and 
keep it in another bottle for the experiment. Pour some of 
this lime-water into a glass, and breathe through a tube into the 
water ; you will find, after a little time, that the lime-water has 
become quite milky. The reason is that the carbonic acid which 
came out from your lungs has united with the lime of the lime- 
water, and formed carbonate of lime, or chalk. After standing 
a little while, the water will become clear, the chalk having set- 
tled at the bottom in a fine powder. 

The quantity of carbonic acid which we breathe out in twen- 
ty-four hours is considerable. It is calculated that a full-grown 
man breathes out in twenty -four hours over two pounds of 
carbonic acid, which is equivalent to half a pound of solid 
carbon, or charcoal. He throws off, therefore, from his lungs, 
in the course of a year, nearly 200 pounds of charcoal — con- 
siderably more than his weight, even if he be quite a large 
man. 

As all animals, of every size, from the elephant down to the 
smallest insect, are constantly breathing out carbonic acid gas, 
the supply of this gas from this source must be very great. 

All animals also take in oxygen from the air with every 
breath. It goes into their blood, and becomes a part of it. 



42 THE AIR WE BREATHE. 

Dangers of bad ventilation. Story of the Londonderry, 

Your blood wonld not keep yon alive if it did not constantly 
take up oxygen as it runs through the lungs. 

See now how the air which you breathe out di£Pers from that 
which you breathe in. That which you breathe out has less oxy- 
gen and more carbonic acid. The nitrogen is not altered. Just 
as much of this comes out as goes in. 

If people are shut up in close rooms, the carbonic acid accu- 
mulates very fast ; and after a while, unless fresh air be let in, 
they will suffer dreadfully for want of oxygen, and may even 
die. 

"We will tell you the story of an emigrant ship called the 
Zondonderry^ which illustrates this. The ship was crowded 
with poor emigrants, and many of them were on deck. A terri- 
ble storm arose, and the captain ordered them all to go below 
into the cabin. There they were very much crowded, and fresh 
air came to them only through an opening in the deck ; and 
since the sea-water dashed down through this in great quantities 
when the waves broke over the vessel, the captain ordered that 
tarpaulin (cloth through which neither water nor air can pass) 
should be nailed over it. The people below immediately suffer- 
ed dreadfully for want of fresh air, and they cried out in their 
distress, but the noise of the storm prevented their being heard. 
At length one of the emigrants succeeded in forcing a hole 
through the tarpaulin. He told the captain that the people 
were dying for want of air. The tarpaulin was pulled up at 
once. Many were abeady dead, and many were just about to 
die. 

All animals, then, in their breathing, and all fires and lights in 



THE AIR AVE BREATHE. 43 

Breathing of leaves. How it differs from that of lungs. 

their burning, add to the carbonic acid in the air and lessen the 
oxygen. What is there, then, to hinder the air from becoming 
all the time more and more laden with carbonic acid, and less 
and less supplied with oxygen ? Just here comes in a wonder- 
ful and beautiful provision of the Creator. He has provided 
the means of taking away carbonic acid constantly from the air, 
and of supplying it all the time with fresh oxygen. And what, 
think you, are the agents that God has appointed to do this 
work ? The leaves. They, too, breathe ; but their breathing is 
different from that of lungs. "While lungs, in their breathing, 
give out carbonic acid, leaves take it in ; and while lungs take 
in oxygen, leaves give it out. Every leaf that you see gleam- 
ing in the sun is busy pouring out into the air oxygen from 
all its little pores, and taking in, at the same time, carbonic 
acid gas. The carbonic acid which the leaves absorb furnishes 
carbon for the growth of the plant. 

There is, therefore, a regular exchange going on between 
leaves and lungs everywhere ; lungs give carbon to leaves, and 
take back oxygen in exchange. 

Questions. — What are the gases in the air ? What is said of the quantity of car- 
bonic acid in the air ? What effect have fires and lights upon the air ? How does a 
candle burning under a glass jar illustrate this ? How does the breathing of animals 
affect the carbonic acid of the air ? Give the experiment with lime-water. What is 
said of the quantity of carbon thro"\vn off from the lungs ? What of the supply of 
carbonic acid to the air from the lungs of all animals ? What is said of the taking- 
in of oxygen by the lungs ? Tell the story of the emigrant ship. What is said of 
the breathing of the leaves ? What is said of the exchange between lungs and 
leaves ? 



44 HYDKOGEi^". THE WATER WE DEIKK. 

Composition of water. 



CHAPTER YIII. 

HYDROGEN. THE WATER WE DRINK!. 

Water is composed of two gases. One of these is oxygen, of 
which you have learned so much in previons chapters ; the oth- 
er is hydrogen. This is the lightest of all gases, and therefore 
the lightest of all substances. Air is nearly fifteen times as 
heavy as hydrogen. A balloon, therefore, filled with this gas 
goes up very swiftly in the air. 

Hydrogen burns with a pale-yellowish flame, giving out much 
heat, and but little light. How strange it seems that oxygen, 
which makes other things burn, and hydrogen, a gas which itself 
burns, combine to form a liquid that puts out fire ! 

"What will seem stranger still to you is that when hydrogen 
gas is burned in oxygen, water is formed. In the burning, the 
oxygen and the hydrogen unite. Not a particle of either of 
them is lost. They merely go into a new condition, uniting to 
form a liquid. In doing this, the bulk of both of them is made 
much smaller. It takes a great deal of these gases to form a 
very small amount of water. 

When hydrogen burns in air, we have the same result as 
when it is burned in oxygen. The hydrogen unites with the 
oxygen of the air, and forms water. It will have nothing to 
do with the nitrogen in the air, but lets it alone, and takes the 
oxygen and combines with it. Several experiments prove that 



HYDEOGEN. THE WATER WE DEINK. 



45 



Catching water from a burning candle. 



Fig. 13. 




water is formed by the burning of hydro- 
gen in air. In Fig. 13 yon see a candle 
placed on a plate under a glass jar, the 
jar being supported by three bits of wood. 
"Water flies off from the flame, and collects 
on the inside of the glass jar. But what 
has this experiment to do with hydrogen ? 
you ask. We will explain it. The tallow 
of the candle is made up of carbon and hy- 
drogen combined. Yes, this lightest of all the gases helps, in 
this case, to form a solid substance. As the melted tallow goes 
up the wick, the air brings oxygen to it, and the heat makes 
this oxygen unite with both the carbon and hydrogen of the 
tallow. By uniting with the carbon it forms carbonic acid. 
This is, you know, a colorless transparent gas, and so you do not 
see it. But there it is in the jar. Uniting with the hydrogen, 
the oxygen forms water, and this goes up in vapor with the 
carbonic acid. But this vapor soon condenses on the inside of 
the glass, because it is cool. The glass therefore becomes dim, 
and after a little time enough water collects to form drops and 
trickle do^^m into the plate. 

Fig. 14, on the next page, represents another experiment. 
Here hydrogen alone is burned without carbon. The bottle 
contains the materials for making the gas, of which we will soon 
tell you. The gas is dried by passing through the large tube, 
and then comes out of the end of the smaller tube, where it is 
lighted and burns. Now, if you should let the hydrogen quietly 
burn without holding any cold glass over the flame, you would 



46 



hydeoge:n'. the water we deink. 



How to prepare hydrogen. 



The philosopher's caudle. 



not see any water; but^ just as in the last experiment, water 
collects on the side of the glass jar placed over the flame, and 
trickles down into the sancer beneath. The hydrogen combines 
with the oxygen of the air, forming vapor of water, and this 
condenses into liqnid drops. 

We will now tell yon how hydrogen is obtained. Put into 
a bottle some bits of zinc, some water, and a little sulphuric 



Fig. 14. 




acid, which is sometimes called oil of vitriol. I*f ow, the oxygen 
of the water unites with the zinc, and this dissolves in the acid, 
while the hydrogen of the water is set free. This rises and 
passes out of the vessel, carrying the air that is in the vessel 
along with it ; and soon, when all the air is driven out, the gas 
comes out alone. In Fig. 15, on the top of the following page, 
is represented what is called the philosopher's candle. The 
zinc, water, and sulphuric acid are in the two -necked bottle. 



HYDROGEN. THE WATER WE DEINK. 



47 



The philosopher's candle. 



Another way to collect hydrogen. 




which is fitted with corks having tubes in them. rig. 15. 

Acid and water are poured into the bottle 
through the tube ending in a funnel, and the 
gas comes out of the bent tube. The gas issu- 
ing from the tube burns just as illuminating gas 
does when it issues from a gas-burner. Much 
caution is required in burning the gas made in 
this way, for a mixture of it with common air is 
explosive. If, therefore, you should hold a light 
to the tube before the air is driven out, you 
might have an explosion, and your bottle might 
be broken, and its contents scattered about. 

In order to collect a considerable quantity of 
this gas, chemists generally make use of another 
sort of apparatus, shown in Fig. 16. The materials are placed 

in the bottle, as before, and 
the gas passes through the 
bent tube into the bowl of 
water, and thence up into 
the glass cylinder, forcing 
the water down just as was 
explained in the prepara- 
tion of oxygen (see Fig. 3). 
In this way several jars 
may be filled with the gas ; 
and so long as the mouths 
are kept under water, the 
hydrogen can not fly away. 



Fig. 16. 




48 



HYDROGEN. THE WATER WE DRINK. 



The lightness of hydrogen. 



How hydn gen burns. 



Fig. ir. 



You remember what was said about pouring carbonic acid gas 
downward. You can not do this with hydrogen. It is so light 
that, the moment it escapes from a vessel, 
it passes directly and quickly upward. You 
can let a jar of carbonic acid gas stand, and 
the gas will not go out; but if you set 
down a jar of hydrogen gas with its mouth 
upward, the gas will at once pass out, the 
air coming in to take its place. If you 
want to pour hydrogen gas from one jar 
into another, you must hold them in the manner represented in 
Fig. 17, the upper jar being the one which is to receive the gas. 




Fig. 19. 



If you set fire to the hydrogen in a jar, Fig. is. 

it burns diflferently according to the way in 
which you hold the jar. If you hold it with 
the mouth upward, the gas, rapidly rising, 
bursts upward with a large flame, as seen in 

Fig. 18. But if you hold it 

with the mouth downward, 

the gas burns very quietly 

as it issues slowly from the 

mouth, as shown in Fig. 19. 

Here the gas does not come 

out freely, for its lightness prevents its coming 

doion out of the jar. 

As hydrogen is so light and thin a gas, it 

has a very curious effect upon sounds. If a 

squeaking toy is made to utter its voice in a 





HYDEOGEN. THE WATER WE DRINK. 



49 



Squeaking toy in hydrogen. 



Music from burning hydrogen. 




Fig. 21. 



jar of hydrogen, as represented in Fig. 20, the Fig. 20. 

sonnd is very ludicrous. 

Musical sounds can be made by burning 
this gas in glass tubes, as represented in Fig. 
21. These sounds vary according to the sizes 
of the tubes. They vary also as you raise 
or lower the tube. Great amusement can be 
afforded by the variety of sounds thus pro- 
duced. 

Burning hydrogen gives but a faint light ; 
but the light of the gas that we burn in our 
houses is very bright, and yet it is partly hy- 
drogen. The reason that it gives so bright a light is that car- 
bon, or charcoal, is united with the 
hydrogen (and on this account it is 
called by the chemist carbureted 
hydrogen). Watch the flame from 
a gas-burner, and you will- see little 
bright points all the time sparkling 
upward. These are occasioned by 
the burning of the minute particles 
of the carbon. 

In the burning of illuminating 
gas, the oxygen of the air, as in the 
case of the candle, unites with both 
the carbon and the hydrogen, form- 
ing, with the carbon, carbonic acid 
gas, and with the hydrogen, water. 
D 




50 HYDROGElSr. THE WATER WE DRmK. 

Illumiuatiug gas. Why gas does not smell in burning. 

And if you hold a glass jar over the burner, the watery vapor 
will condense on the inside of the jar, as in the similar experi- 
ment with the candle. 

"When illuminating gas escapes without burning, it has, you 
know, a very disagreeable odor ; but when it is burned, you do 
not smell it at all. Why ? Because it is consumed by the oxy- 
gen of the air in forming water and carbonic acid, and neither 
of the things formed has any smell. The smell of the gas is 
useful to warn us of danger. If it had no odor, whenever there 
is a leak of gas we would not know it, and might take a light 
into some place where there is a great deal of it. An explo- 
sion would be the consequence, and great harm would be done, 
and perhaps lives would be lost. Since, however, we can smell 
the gas, when it has been leaking we open all the doors and 
windows, and let them remain open for some time before we go 
in with a light. 

The interesting gas hydrogen is never found free in nature, 
but is always combined with some other substance. It is con- 
tained in wood, oils, fats, coal gas, and soft coal ; but by far the 
greatest amount of hydrogen occurs, combined with oxygen, in 
water. Have you ever thought how abundant water is ? " It 
covers three-quarters of the earth's surface, in the form of ocean, 
lake, and river ; and in the higher latitudes, snow, ice, glacier, 
and iceberg. Kising in the form of vapor, it produces, by con- 
densation, clouds, fog, mist, rain, and snow. In the vegetable 
kingdom it is ever present, varying in quantity from ninety-nine 
per cent, down to fifteen or twenty. Dry wood contains twen- 
ty per cent, of moisture. Animals consist largely of water ; an 



HYDEOGEN. THE WATER WE DRINK. 51 

Hard water. How water may be purified. Distilled water. 

average man weighing 150 pounds contains about 116 pounds of 
water. The rocks contain it ; some hold it in large qnantity. 
Gypsum contains twenty per cent, of water, and even hard rocks 
like granite contain a fraction of a per cent." — C. F. Chandler. 

The water we drink is not pure oxygen and hydrogen. Ow- 
ing to the power it possesses of dissolving minerals, spring-wa- 
ter and river-water contain small quantities of common salt, lime- 
stone, gypsum, and other substances dissolved in them. These, 
together with organic matter resulting from the decay of vege- 
table or animal substances, constitute the impurities of drinking- 
water. In some portions of the country, where the water runs 
over limestone rocks, much lime is taken up by the water, which 
is then said to be hard. Other impurities of water are mud, 
clay, and even fine particles of sand. 

Pure water is obtained in several ways ; one of the simplest is 
by filtration : the water is poured into an apparatus containing 
some porous material, such as charcoal, which separates many of 
the impurities as the water trickles over it. Water may also be 
purified by boiling it, particularly if its impurities are of animal 
and vegetable origin, these being especially injurious. Water is 
best freed from these various impurities by distillation, an oper- 
ation in which the water is converted by heat into steam in one 
vessel, and this steam is cooled down again to liquid water in 
another vessel. This plan is used on shipboard : sea-water being 
distilled is rendered fit for drinking. The water obtained by 
coohng the steam is called distilled water. 

When the amount of the mineral substances is large, or the 
ingredients are rather uncommon, the waters have a saline or 



52 HYDEOGEN. THE WATEE WE DEINK. 

Mineral waters. Composition of water. 

peculiar taste, and are called mineral waters. Such waters may 
be valuable for their medicinal properties, or as sources of the 
special substances they contain. The mineral waters of Sarato- 
ga, ISTew York, and the various hot and mineral springs of Yir- 
ginia, California, and Ohio, as well as of different parts of Eu- 
rope, are examples of medicinal waters. Some of these waters 
contain a gas dissolved in them, which bubbles up continually, 
and makes the water very pleasant to drink. This gas is car- 
bonic acid, about which you learned in Chapter YI. We will 
speak of sea - water later ; meanwhile, let me remind you what 
we stated at the beginning of this chapter, viz., that water is 
composed of two gases — oxygen and hydrogen. 

Questions. — Of what is water composed ? What is said of the lightness of hydro- 
gen ? What is formed when hydrogen is burned in oxygen ? What is said of burn- 
ing hydrogen in air ? What two things are formed when a candle burns ? How can 
we obtain hydrogen? Describe the philosopher's candle. State the contrast be- 
tween hydrogen and carbonic acid. Tell about the squeaking toy. What is said of 
burning hydrogen in glass tubes ? Why does hydrogen burn with a pale flame and 
illuminating gas with a bright one ? What are formed in the burning of illumi- 
nating gas, and how ? Why does the smell of this gas disappear in burning ? How 
is this smell useful ? What is said of the abundance of water ? What of the water 
we drink ? In what ways may water be purified ? What is distilled water ? What 
are mineral waters ? Name some of the localities in which they occur. What gas 
makes mineral waters pleasant to drink ? 



COMBUSTION. 53 



Meaning of combustion. Rusting of iron. 



CHAPTER IX. 

COMBUSTION. 

You have already learned considerable about burning, or com- 
bustion, but we will now study the subject more closely. 

What we usually call combustion attends the union of oxygen 
with some other substances, either solid or gaseous, as with car- 
bon and hydrogen. Thus, in the combustion of charcoal, the 
oxygen unites with the charcoal ; when hydrogen burns, oxygen 
unites with the hydrogen ; and when iron burns, as in a jar of 
oxygen gas, oxygen unites with the iron. 

But we commonly use the term combustion only when it is 
accompanied with heat and light, and yet the union of oxygen 
with other things often takes place without producing any light. 
This is when the union takes place slowly. Thus, when iron 
rusts, the oxygen of the air unites with it, but so slowly that no 
light is given out ; there is heat, but so little of it that it can 
not be felt, because the union is so slow. It is a very slow fire. 
Now, this same union takes place when iron or steel burns in 
oxygen, and then we have both heat and light, because the 
union is so quickly effected. It is really a combustion in both 
cases, and the only difference lies in the time consumed. When 
a man, then, paints his iron fence to keep it from rusting, he 
really keeps it from getting burned. 

Tou can understand now how water puts out fire. It shuts 



54 coiviBUSTioisr. 



How fires are extinguished. Keeping fire by covering it up. 

out the oxygen of the air from the burning substance. It acts 
much as the paint acts on the iron. But perhaps you will 
say that there is a plenty of oxyge'a in water, since it is com- 
posed of oxygen and hydrogen, and throwing water on fire is 
therefore giving it oxygen. This is not so. Oxygen is not in 
water simply as oxygen ; it has formed a neio substance with 
hydrogen, and the hydrogen in this new substance holds on to 
the oxygen, so that the fire can not get a particle of it. 

But this is not all. Water operates in another way in putting 
out fire. It takes from the burning substance the heat needed 
to keep it afire. This heat is spent in turning the water into 
vapor or steam. 

When you put out a fire by smothering, as it is said, you shut 
out the oxygen of the air, and the burning stops merely for the 
want of oxygen. So, if a person's clothes take fire, you need 
not wait to get water, but wrap the person at once with what- 
ever is at hand — a coat, a rug, or any thing else — thus shutting 
out the oxygen of the air. An extinguisher put over a candle 
puts out the light by keeping oxygen from coming to it. 

But perhaps you will say that people who burn wood cover up 
fire to keep it, and why does not the shutting-out of the oxygen 
of the air put out the fire in this case ? Simply because all of 
the air is not shut out ; if it were, the fire would not keep. The 
keeping of the fire depends on letting in some air through the 
ashes, so that there may be a slow burning. 

As fire, or combustion, results from the union of oxygen with 
the burning substance, the more freely you bring the oxygen to 
it, the brighter wiU be the fire. When you blow a fire with bel- 



COiyiBUSTION. 55 



Blowing a fire. Blowing out a candle. 

lows to make it burn, you increase the supply of oxygen, and 
feed it to the fire faster than it would come without the blow- 
ing. The coals, perhaps, are just kept alive, as we say, by the 
little oxygen that is in the still air about them. You blow them, 
and you bring a great deal more air, and therefore of oxygen, to 
them, and they brighten up at once. If you could blow nitro- 
gen alone, or carbonic acid gas, upon them, it would put them 
out, for this would keep away from them the oxygen of the 
air. 

A lighted candle is kept burning by the oxygen of the air, 
and the more oxygen, therefore, that you bring to it, the more 
brightly it should burn. Why, then, do you blow a candle to 
put it out ? A boy once supposed that he had given a suffi- 
cient explanation in saying that the breath knocks the flame 
right over. The true explanation is this : A certain amount of 
heat is needed to keep up the burning. Now, the air may be 
thrown so rapidly against the candle as to carry off enough 
heat to stop the combustion; it carries off heat in the same 
manner that air cools your face when blown against it by a fan. 
In blowing a fire just starting, we have to be a little careful, or 
we may blow away too much heat from the fire. 

There are some contrivances for making our lights burn very 
brightly. Their object is to supply oxygen rapidly, but at the 
same time steadily, and not by sudden blasts. One of these con- 
trivances is a glass chimney. See how this operates. The hot 
gas and vapor that come up from the light are confined in the 
chimney instead of spreading out in the air around ; they pass 
up, therefore, very rapidly through the chimney, and so make a 



56 COMBUSTION. 



Operation of lamp-chimneys explained. How things are set on fire. 

strong drauglit.^ This makes the air come rapidly to the light 
from below, and of com^se a great deal of oxygen comes to it in 
a little time. 

You see how great the draught is if you hold your hand over 
the top of the chimney ; you will feel a current of hot gas a*nd 
vapor striking it. You must be careful not to put your hand 
too near. The whole of this current does not go straight up, 
but it spreads out as soon as it escapes from the chimney, so 
that, at a little distance, your hand feels only a small part of the 
current, and that is somewhat cooled. 

Another contrivance is to use a flat wick instead of a round 
one. You see that siich a wick presents a larger surface to the 
air than a round one, and therefore more of it can be reached by 
the oxygen. 

Some wicks are made annular, the air being admitted on the 
inside as well as the outside of the circle. A very bright light 
is obtained in this way. 

Observe now how we start a fire. We usually do it by apply- 
ing something burning to the combustible substance. Thus we 
set fire to wood by burning paper or shavings. In like manner, 
when we open a gas-burner, we put to it a burning match, and 
thus set fire to the stream of gas as it comes out. But think a 
moment what sets fire to the match. It is by rubbing it, you 
win say. But how ? The friction creates heat enough to cause 
the oxygen to unite with the phosphorus, and the union is 
quick enough to make light as well as heat. Thus you see heat 

* The manner in which this draught is produced is explained fully in the chapters 
on Heated Air and Chimneys, in the Third Part of the Child's Book of Nature. 



coMBusTiojsr. 57 



Why some things burn more easily than others. 



and chemical action cause what we call fire. This is very oft- 
en seen in kindling a w^ood fire. ^ Suppose you have a bed of 
coals beneath the w^ood, how is the wood set on fire ? The coals 
heat the wood, and, after a little time, they make the wood hot 
enough to ignite. 

Some substances ignite at a lower temperature than others; 
the degree of inflammability is determined by the attraction of 
the substance for oxygen. Phosphorus, having a very great 
attraction for oxygen, takes fire very easily, and requires great 
care in handling. 

Some substances can not be burned at all. Gold is one of 
them. Iron, you have seen, can be burned — that is, it can be 
made to unite with oxygen ; but you may expose gold to the 
hottest fire, and it will only melt ; it will not burn. It will not 
unite with the oxygen. And what is true of these two metals 
in regard to quick combustion, is also true of them in regard 
to the slow combustion mentioned in the first part of this chap- 
ter. Gold never rusts in the air — that is, it is not consumed 
with a slow fire. 

Questions. — What usually occurs in combustion ? Illustrate the difference between 
quick and slow combustion. How does water put out fire ? Why does not the oxy- 
gen in the water make the fire burn ? What is said of putting out fires by other 
means ? Explain the effect of blowing a fire with bellows. What would be the ef- 
fect if you should blow nitrogen or carbonic acid upon a fire ? Explain the opera- 
tion of a glass chimney on a lamp. If you hold your hand over the top of the chim- 
ney, what strikes agamst it ? What is the advantage of a flat wick ? What of an 
annular one ? When we set fire to any thing, what starts the fire ? Give the illustra- 
tion of the match ; also of the wood set on fire by coals. What is said about the at- 
traction of phosphorus for oxygen ? What about the attraction of gold for oxygen ? 



58 GAS-MAKING AND GAS-BUKNING. 

Chemistry of a candle. 



OHAPTEE X. 

GAS-MAKING AND GAS-BUENING. 

Every candle or lamp is a gas factory. 

We have told you that both, carbon and hydrogen occnr in 
tallow. They are united there as a solid compound ; bnt, when 
the candle burns, this solid becomes liquefied by the heat at the 
foot of the exposed part of the wick. See what a cup of melted 
tallow we have there. It is curious to observe how this cup is 
formed, and kept just so, all the time the candle is burning. 
The heat of the burning wick melts the tallow, but that which is 
nearest the wick is, of course, melted first. This keeps a raised 
edge all around. If the wick gets bent over to one side, it is apt 
to melt this edge on that side, and so some of the melted tallow 
runs out of the cup and down the side of the candle. 

But the melted tallow at the foot of the wick must go up 
the wick to be burned. How is this effected ? It rises because 
there is an attraction between the fibres of the wick and the 
liquid. This kind of attraction is commonly called capillary 
attraction, because it was first observed on putting the ends of 
very small tubes into water, or almost any liquid. The smaller 
the tube, the higher the liquid ascends in it. The small tubes 
are called capillary tubes, because their bores are as fine as hairs, 
cajpillus being the Latin word for hair. 

The liquid tallow, when it comes to the lower part of the 



GAS-MAKING AND GAS-BTJRNING. 



Flame of a candle burning gas. Unburned gas inside of it. 

flame, is changed by the heat into a gas, and the burning of 
this gas makes the flame. What is this gas ? It is a eompoimd 
of hydrogen and carbon. It is much the same gas as that whicli 
comes out of a gas-burner. 

The flame of a candle is a curious thing to examine. It is 
not really all flame ; a part of it is gas, which is not burning. 
If you look carefully at the flame when the air is still, you will 
see that it is hollow, like a shell. JSTow, the space inside of this 
shell is filled with e^as not vet afire; this 

^ , '^ ' . Fig. 22. 

looks dark, as you see it through the bright 
shell of flame. 

You can prove that this dark inner part is 
gas by some very pretty experiments. Take 
a small glass tube, and put one end of it, as 
shown in Fig. 22, in the very middle of the 
flame — in the dark part. Some of the un- 
burned gas will pass ofi through the pipe, 
and you can set it on flre as it issues at the other end. Every 
candle, then, is a gas factory, and you can take the gas from 
it in pipes, as we do from the large gas factories that supply 
towns and cities. 

There are really three parts to a flame, as shown in Fig. 
23, on the following page, the burning shell being composed 
of two parts. The outer part of the shell, 1, is not so bright 
as the inner part, 2. As the gas, 3, rises from the melted tal- 
low, some of it continually passes into the shell, 2, where the 
hydrogen burns very briskly, and sets on flre the flne parti- 
cles of carbon. These particles, thus lighted and beginning 




60 



GAS-MAKING- AND GAS-BUENESTG. 



Cause of the brightness of flames. 



Illumiuating gas. 



Fig. 23. 




Place some shav- 
ings in a glass tube 
closed at one end, 
and fitted with a 
cork and a bent 
glass tube, as shown 
in Fig. 24. Then heat the shavings, 
and soon illuminating gas will pass out 
through the tube, and you can light it. 
In place of shavings, you might use soft 
coal, and then you would imitate the 



to burn, make that part of the flame bright. 
As they pass into the outer part of the 
flame, 1, their burning is finished by a per- 
fect imion with oxygen, forming carbonic 
acid. 

The brightness of the flame of illumina- 
ting gas is due to these same particles of 
red-hot carbon. Alcohol burns with a 
pale flame, because it is not very rich in car- 
bon ; turpentine, on the other hand, burns 
with a very smoky flame, because it contains 
a great deal of carbon. 

The illuminating gas burned in our dwell- 
ings is usually made from coal. You can 
make gas for yourself in a very simple way, 
and the experiment will help you to un- 
derstand its manufacture on a large scale. 

Fig. 24. 




GAS-MAEING AND GAS-BUENING. 



61 



Bursting bubbles. 



Burning oxygen and hydrogen together. 



method of making gas in large gas-works. Large iron vessels, 
or retorts, are used, inclosed in furnaces. Into these retorts 
coal is put, and the heat drives off the gas. It is impure as 
it comes off, and must, therefore, be purified before it is sent 
through the distributing pipes. 

We have spoken now and then of explosions taking place 
with gases. Now, what is such an explosion? What takes 
place ? It is a sudden burning of a quantity of gas at once, and 
the gas, in burning, unites with oxygen. Thus, if we mix oxy- 
gen and hydrogen, and then set fire to the mixture, there is an 
explosion. The whole of the hydrogen burns at once in the 
oxygen, water forming, just as when hydrogen quietly burns at 
the end of a tube. When coal gas, escaping from a leak, ex- 
plodes on bringing a light to it, the explosion is produced by 
the sudden union 



of the gas with 
the oxygen of the 
air. 

Tou can ex- 
plode mixtures 
of oxygen and 
hydrogen safely 
in many ways : 
a neat way is 
shown in Fig. 25. 
The man holds 
an air-tight bag 
filled with the 




62 



GAS-IVIAKING AND GAS-BURNINO. 



The oxyhydrogen blow-pipe of Dr. Hare. 



mixture of oxygen and hydrogen above spoken of, and a to- 
bacco-pipe is connected with the month of the bag. In this 
month is a stop -cock, so he can let ont the gas as he pleases. 
By placing the bowl of the pipe in some soap-and-water, he lets 
out some of the gas, and so forms a bubble. Now, since hydro- 
gen is so very light, and two-thirds of the gas in the bubble is 
hydrogen, the bubble flies upward. As it flie^, the young man 
touches it with a light, and it explodes. In trying this experi- 
ment, caution is necessary, lest the light be brought near the 
bowl of the pipe, and thus explode all the gas in the bag. 

If we let a small stream of oxygen gas and another of hydro- 
gen burn together, a most intense heat is produced. It will melt 
and burn up the hardest substances. Fig. 26 represents an ar- 
rangement for burning these two gases together. The oxygen 

is in the bag, with 



Fig. 26. 




a weight upon it 
to make the gas 
pass out through 
the pipe. The 
end of the pipe is 
brought close to 
the flame of the 
hydrogen, which 
comes up from a 
bottle which you 
see below. For 
working on a lar- 
ger scale, the gases 



GAS-MAKING AND GAS-BrRNING. 63 

Burning iron wire. The Drummond light. 

are usually kept in iron cylinders, and a donble-tubed safety jet 
is employed. Such an arrangement is called an oxyhydrogen 
blow-pipe, and was invented by Dr. Hare, of Philadelphia, about 
seventy-five years ago. 

If you hold with a pair of pincers a piece of very small copper 
wire in the burning jet of these two gases, it will burn with a 
beautiful green flame. If you use iron wire, bright sparks will 
fly prettily. The oxygen unites, in this intense heat, with the 
hydrogen to form water, and with the metals to form bodies 
called oxides. They are called oxides because they contain oxy- 
gen. Iron rust is oxide of iron^ and lime is the oxide of another 
metal of which you will learn more hereafter. 

The Drummond light, of which you have perhaps heard, is 
made by causing the burning gases, hydrogen and oxygen, to 
strike against a piece of lime. The lime becomes intensely 
heated — in fact, white-hot ; and shines with a dazzling brilliancy 
resembling that of the sun. The light receives its name from 
its discoverer, Lieutenant Drummond, of the English navy. It 
is used to illuminate buildings at night ; in theatres, and in other 
places where a brilliant light is required. 

Questions. — What two substances are in tallow ? Describe the melting of the tal- 
low as the candle burns. Why does the melted tallow go up the wick ? What is 
the gas made from the melted tallow ? Describe the flame of the candle. How can 
you prove that the dark inner part of the flame is gas which is not yet on fire ? Whr;t 
is said of illuminating gas ? Describe the making of gas as represented in Fig. 24. 
Describe the making of it at the gas-works. What is said of explosions of gases ? 
Describe the experiment represented in Fig. 25. Describe the arrangement in Fig. 26. 
Tell about the burning of copper and iron in the flame of hydrogen and oxygen. 
What is the substance formed in burning iron ? What is the Drummond light ? 



G4 STEiKma fire. 



The spark, in striking fire, burning iron. 



CHAPTEE XI. 

STEIKINa FIEE. 

Every body has seen fire struck from tlie heel as it hits upon 
a stone, and yet how few know exactly what is done ! They see 
the spark, and are satisfied with saying that it is striking fire. 

But what is the spark? It is something more than a mere 
show of light; it is a burning substance. "What is this sub- 
stance ? It is a bit of steel or iron from a nail in the heel ; this 
is knocked off as the heel strikes the stone, and there is heat 
enough made by the blow to set it on fire. 

The spark, then, is a particle of burning iron. But how does 
it burn ? Precisely as the steel burned in the jar of oxygen gas. 
There is oxygen in the air, and the blow of the heel upon the 
stone makes the bit of iron so hot as to cause the oxygen of the 
air to unite with it at once ; and they unite so quickly that they 
light up, and so the little mite of iron flies off a bright spark. 

The spark falls and goes out. It is so small that you can not 
find it. But what is it ? Is it iron ? IsTo, for it has been burned. 
And what is it to burn iron ? It is to make oxygen unite with 
it. The fallen spark, then, is not iron, but iron and oxygen 
united — that is, an oxide of iron. 

Before lucifer - matches were invented, every family was in 
possession of a tinder-box for the purpose of striking a light. 
The apparatus consisted of a piece of steel, a fiint, some haK- 



STRIKESra FIEE. 65 



The tiuder-box. Indian method of getting fire. 

burned rags in a tin box, and some matches, which were splin- 
ters of wood tipped with a little sulphur. The way in which a 
light was obtained was this : The flint was struck upon the steel 
held over the tinder till the tinder was set on fire by a spark 
from the steel ; then, applying a match to the burning tinder, 
the sulphur on its end took fire. It often was necessary to 
work some time to get a light in this way, and a person's pa- 
tience was sorely tried. 

The invention of lucifer-matches, by which we can produce 
a light in a moment, has caused all the tinder-boxes to be laid 
aside. 

The method which the savage formerly adopted for obtaining 
fire was more laborious than that of the tinder-box. He sharp- 
ened a piece of hard wood to a point, and very rapidly turned 
this, after the manner of a drill, against a soft piece of wood, 
having some light chips around it. It required great practice to 
enable one to move the pointed stick with sufficient rapidity to 
set fire to the chips. Any one can make two sticks quite warm 
by rubbing them together, but to make them hot enough to set 
any thing on fire is a different matter. The Indian, therefore, 
must have thought the tinder-box a wonderful invention when 
he first saw the white man use it. 

In all these cases the fire is produced in the same way. It is 
the union of the oxygen of the air with the wood, with the steel 
of the tinder apparatus, and with the phosphorus of the lucifer- 
match, that makes the fire; and it is heat in each case that 
causes the union. The match takes fire the most easily, be- 
cause but little heat is required to make the phosphorus unite 

E 



66 



STRIKma FIRE. 



Machinery taking fire by friction. 



■ The knife-grinder. 



with the oxygen. You can produce enough heat for this by a 
slight rubbing. It is supposed by some that many of our fires 
are occasioned by matches carelessly left about : they should 
always be kept securely shut up in boxes. 

What you see on the end of a match is not phosphorus alone, 
but a mixture of this with some other substances, which make 
it burn more readily than if it were alone. The reason is, that 
they have considerable oxygen in them. The more oxygen 
there is to unite with the phosphorus, the more violently it 
will burn; and, in lighting the match, the friction makes the 
phosphorus unite with the oxygen in these substances, in addi- 



Fig. 27. 




tion to that which is in the 
air. 

• Machmery is sometimes set 
on fire by the heat occasioned 
by friction — that is, the iron 
part of it becomes so hot that 
it heats the wood part suffi- 
ciently to make the oxygen 
of the air unite with it. If 
the axles of railway -cars are 
not kept well oiled, the heat 
produced by the friction sets 
the little oil that is in the 
axle-boxes on fire — that is, 
makes the oxygen of the air 
unite with it. 

As the knife-grinder, with 



STRIKINQ FIRE. 67 



Knife-grmding. 



liis rapidly revolving wheel or disk of stone, makes sparks fly 
off, lie really bums np a part of the knife he is grinding. In 
Fig. 27, on the preceding page, is represented a machine for 
grinding cutlery. A disk of soft iron is made to revolve at the 
rate of 5000 times a minute. If a hard file be held against the 
edge of this disk, the rapid friction will burn up that part of 
the file which touches the disk, and a shower of sparks will be 
thrown upward. Here you have the same effect produced as 
when you strike fire with your heel : the union of the oxygen 
w^ith particles of the file makes the sparks. 

Questions. — In striking fire, is the spark merely light ? "What is it ? Give the 
comparison between this and the burning of iron in a jar of oxygen gas. What is 
the spark after it has fallen and gone out ? What is said of the old-fashioned tinder- 
box ? What is said of the Indian's mode of obtaining fire ? AYhat makes the fire in 
all the cases mentioned ? What is said of accidental fires by matches ? What of the 
substance on the ends of matches ? What of setting machinery on fire ? What of 
setting oil on fire in axle-boxes ? Tell about the knife-grinder. 



68 ANIMAL HEAT. 



Heat of our bodies produced by combustion. This compared to the burniug of a candle. 



CHAPTER XII. 

ANIMAL HEAT. 

What is it that makes your body warm ? Clothes and fires, 
perhaps yoii will say. No ; they help to Tteep you warm, but 
they do not make you so. The heat that makes you warm is 
produced in your own body, and clothes and fires only serve to 
keep it in. The heat in you is made by the combustion that 
is going on everywhere in your body. It is a real fire, though 
there is neither flame nor light. 

This is one reason you can not live without oxj^gen. This gas 
is needed to keep up the fire in your body, just as it is needed 
to keep all the fires and lights burning. 

The burning in your body is like that of a common candle 
in the results of the combustion. The oxygen of the air unites 
with the carbon of the tallow-candle to form carbonic acid, and 
with the hydrogen to form water. So, also, the oxygen that 
goes into your lungs and enters the blood, unites with the car- 
bon of your body to form carbonic acid, and with its hydrogen 
to form water. 

But in what parts of the body does the oxygen find the car- 
bon and the hydrogen ? It finds them everywhere. They make 
up, in part, the very substances of your body, as they do the sub- 
stance of the candle. The blood circulates everywhere, to the 
very ends of your fingers, and it carries in it the oxygen that it 



ANIMAL HEAT. ' 69 



Where the fire in our bodies is. A comparison and a diflfereuce. 

takes from the air whicli comes into your lungs. And the 
warmth in your fingers, as well as everywhere else, is made by 
the union of the oxygen with the hydi^ogen and the carbon 
present. 

But you will ask, "Are carbonic acid gas and water formed in 
the very ends of my fingers as they are in the burning candle f 
Exactly so. "What becomes of them?" you will ask again. 
" Do they go off from my fingers into the air as they do from 
the candle ?" Perhaps some of the water does. " But the car- 
bonic acid gas, what becomes of that ?" It goes in the blood to 
your lungs, and there is breathed out into the air. 

The breathing-out of carbonic acid gas has already been de- 
scribed in Chapter YII. This gas that you breathe out comes, 
then, from all parts of the body. It is amusing to think that, 
when you breathe into lime-water and make chalk, a part of the 
gas you make it with has come from the very ends of your 
fingers and toes, and has been made there by a sort of fire. 

Some of the water, too, formed by this fire in your body goes 
out in your breath ; and it goes out in vapor, just as it goes up 
from a burning candle. This vapor will collect on a cold glass, 
if you breathe on it, in the same manner as the vapor from a 
candle condenses on a glass jar put over it. 

The candle burns up; so does your body. The fire is con- 
suming every part of your body all the time. But there is one 
great difference between your body and the candle in this mat- 
ter. The candle is soon all gone, for there is no making up for 
•what is consumed. But your body remains about the same day 
after day, notwithstanding that some of it is burning up all the 



TO ' ANIMAL HEAT. 



Some of our food fuel for the fire that burns in us. 



while. This is because there is in the body a constant supply 
of new substance in place of that which is burned. Your body, 
then, is more like a lamp fed by a fountain of oil than like a 
candle. 

A part of the food we eat is fuel to keep up the fire in us — 
that is, it goes to supply the carbon and hydrogen continually 
burned up in our bodies. Some kinds of food furnish a great 
deal of carbon and hydrogen, and so are of great use in keep- 
ing up the fire in us. Sugar is one of these; fat is another. 
Inhabitants of very cold climates — the Esquimaux, for instance 
— eat large quantities of fat meat and oil, because they are of 
use in keeping them warm. They need food that has a great 
deal of charcoal in it for fuel, so that a good fire may be kept 
up in them to guard against the extreme cold of the climate. 
They are very fond of this kind of food. A captain of a vessel 
once invited one of these people to dine with him. His guest 
declined to take the coffee and wine which were offered him, 
but, seeing an oil - can near by, he took it up and drank all the 
oil. That was a drink he had learned to like, for he had been 
used to drink it to keep himself warm. But the coffee and wine 
he did not think of much account. 

The carbonic acid which a full-grown man breathes out from 
his lungs in a year contains about 200 pounds of charcoal. 
I^ow, all this carbonic acid comes from the fire within his body, 
and in this fire this large quantity of charcoal unites with oxy- 
gen. Where does all this charcoal come from ? He swallows 
it in his food — in the sugar, bread, meat, fat, etc., which he eats# 
You swallow every year an amount of charcoal which would 



ANIMAL HEAT. 71 



How exercise warms us. Our bodies heat the air around us. 

weigh more than you do, and this is burned up within you to 
keep you warm. 

You know that when you run or play very hard, yoa become 
heated. This is because your heart beats more quickly than 
when you are still, and the blood flows very rapidly in your 
arteries and veins. At the same time, you breathe quickly. 
Now, the quick breathing causes more air, and therefore more 
oxygen, to enter the lungs ; more oxygen, of course, gets into 
the blood, and, as the circulation is quickened, the oxygen is car- 
ried everywhere more rapidly ; the fire, therefore, burns more 
briskly in every part of the body. 

Did you ever think that your body is always giving out heat 
to the air around you? The air is almost always cooler than 
your body, even in very hot weather. You are uncomfortably 
warm in a hot day, not because the heat of the air goes into 
your body, but because your body does not give off enough heat 
to the air. A great many persons, therefore, crowded together 
give out a great quantity of heat. We often see this illustrated 
in large parties. The rooms are comfortable at first, when only 
a few persons are gathered ; but when the rooms are crowded, 
the air is uncomfortably warm. 

If you stand out in the cold without sufficient clothing, you 
become chilled, because the cold air is taking away heat so fast 
from all the outside of your body. 

How can you remedy the difficulty? In two ways. One is 
to make the fire in you burn more briskly ; this you can do by 
exercising in some way — ^running, jumping, working. This will 
make your blood circulate more rapidly, and you will breathe 



72 ANIMAL HEAT. 



Difference in the coverings of animals in cold and hot climates. 

more quickly, so that more oxygen will go into the blood. You 
have seen workmen in cold weather strike their arms across the 
body, letting the hands come over upon the back. This is to 
make the blood go more freely to the very ends of the fingers, 
that there may be an abundance of oxygen there to unite with 
the carbon and hydrogen, and so produce sufficient warmth. 

Another way to remedy the difficulty is to put on more cloth- 
ing, which keeps in the heat constantly generated within you. 
You need more clothing when- you are riding in the cold than 
when you are walking or playing, because the fire is not so brisk 
when you are still as when you are exercising. 

Animals living in cold climates have clothing provided for 
them by the Creator fitted to keep in the heat which is made in 
their bodies : they are clothed with f m^s for this purpose. Con- 
trast the polar bear and the elephant in this respect. The bear 
has a good furry coat ; while the elephant, that lives in a warm 
climate, has only a few straggling hairs upon his skin. 

Questions. — What makes the heat in your body ? What is said about not being 
able to live without oxygen ? What does the oxygen that goes into your lungs unite 
with to produce heat ? Where does it go to find the substances with which it unites ? 
How do the water and the carbonic acid formed in the combustion of the body es- 
cape into the air ? Give the comparison between the candle and your body in rela- 
tion to the vapor produced by this combustion. What is said of food as fuel ? Tell- 
about the Esquimaux. Relate the anecdote of the captain's guest. Explain why you 
become so much heated on exercising briskly. What is said about our giving out 
heat to the air ? What about many people being together ? Why are you chilled 
when standing in the cold without sufficient clothing ? What ways are mentioned 
of getting rid of the difficulty ? What is said about animals living in cold climates ? 



rRON-RUST, POTASH, AND LIME. 73 

Composition of rust. Its union with iron. 



CHAPTEE XIII. 

IRON-RUST, POTASH, AND LESIE. 

"Which do you think is the heaviest — a piece of iron, or the 
same after it is rusted ? The iron, you will perhaps say. Why ? 
Because the rust eats it, says one. And, says another, people 
always say of a stove-pipe, when the rust has made holes in it, 
that it is rusted away. But let us look at this. When iron 
rusts, oxygen is added to it or is united with it, and, of course, 
it will weigh more with this addition. To be sure, oxygen is 
a very light substance, nearly as light as air, but it has some 
weight, and this weight is added to the iron when the iron 
turns to rust; and it is to be remembered that a very consider- 
able bulk of oxygen is added. Whenever you see iron -rust, 
then, remember that a large quantity of this gas is condensed 
into a very little space ; and being thus united with iron, it is 
no longer a gas, but a part of a solid substance. 

But what we commonly call rust contains something besides 
oxygen united with the iron : there is water in it. It does not 
show itself as water, for the rust is dry. How is this ? The wa- 
ter in the rust is no longer a liquid, just as the oxygen in it is 
not a gas. Both the liquid and the gas become parts of the 
soHd substance. 

Most metals will, like iron, burn, or, in other words, will unite 
with oxygen ; but there are some metals that will not burn at 



74 

Potassium not a simple substance. Discovered by Sir Humphry Davy. 

all. This is because they have no liking or attraction for oxy- 
gen. Gold is one. If yon apply heat enough to melt it, it will 
not take any of the oxygen of the air to itself. Hence it is so 
very useful in gilding articles, for it never tarnishes — that is, 
never rusts. On the other hand, some metals like oxygen so 
well that they unite with it at once whenever oxygen touches 
them, and sometimes burn with violence. Potassium is one of 
them. This is a metal that has never been found anywhere. 
How, then, you will ask, do we know that there is such a metal ? 
It was discovered by a celebrated English chemist. Sir Hum- 
phry Davy. Davy, by-the-way, was once a poor boy ; but he 
became a great man, because he was always studying and think- 
ing about what he learned. 

By means of some very ingenious experiments with potash, a 
substance with which you are probably familiar, Davy proved 
that it is not a simple substance, and he obtained from it the 
metal potassium. He found that potash is composed of oxygen, 
water, and a metal, in much the same way as iron-rust is made 
up of oxygen, water, and iron. Potassium, when once obtained, 
is very difficult to keep, because it is continually uniting with 
the oxygen of the air ; but the air may be shut out by placing 
the potassium under a liquid called naphtha, and this is com- 
monly done. You understand now why the metal has never 
been found in the earth by itseK, as gold and silver are ; it is 
always combined with some other substance. 

Most of the metals you are acquainted with are hard and 
heavy, but potassium is quite different; it has a bluish -white 
color, is quite soft, so that you can mold it* between the fingers 



IRON-EUST, POTASH5 AND LIME. 75 

A metal that swims aud takes fire on water. 

almost like wax when it is a little warm, but it is brittle wlien 
cooled down to the freezing-point of water. It is a very. light 
metal, so light that it will swim on water. 

If potassium be left exposed to the air, it tarnishes at once, 
and in a short time is all turned to potash, the oxygen of the air 
uniting with it. 

If you throw a little piece of it upon water, it steals away the 
oxygen from the hydrogen of the water, and flies about the sur- 
face, burning with a beautiful violet flame, as Fig. 28. 
represented in Fig. 28. This flame is the hy- 
drogen set free by the union of the potassium 
with the oxygen of the water. The hydrogen 
bnrns because this union is made quickly, and 
so produces heat enough to set fire to the hy- 
drogen. The color is given to the flame by 
the potassium. If this metal be thrown upon ice, the same 
burning will occur. 

It seems very strange to us that a metal should float on water, 
and burn up while it is floating. "When Sir Humphry Davy 
made the discovery, he astonished every body. Even his broth- 
er-chemists were astonished. It is related that Davy put a small 
piece of the newly-discovered metal into the hand of his friend 
Dr. WoUaston, a celebrated chemist, and Dr. WoUaston spoke of 
it as being quite heavy. Davy soon showed him his mistake by 
throwing it into water. The philosopher expected to see it sink 
like lead, and was utterly surprised to see it both float and burn. 

There are several other metals which float and burn on water, 
but we will only describe one of them, called sodium. Sodium 




76 IRON-KUST, POTASH, AND LIME. 

Quicklime. Calcium. Slaked lime. 

is made from soda, mucli as potassium is obtained from potash, 
and it was also discovered by Sir Humphry Davy, about sev- 
enty years ago. Sodium, when thrown upon water, decomposes 
it, taking the oxygen from the hydrogen, as potassium does. 
A hissing sound is produced, but the escaping hydrogen will 
not burn unless the water be hot. When it does burn, the flame 
has a beautiful yellow color, given to it by the metal. 

There are great quantities of this metal in the world, for it is 
one of the ingredients of common salt. Like potassium, it is 
never found alone, but is always united with oxygen or some 
other substance. 

Lime was supposed to be a simple substance or element before 
the discoveries of Sir Humphry Davy. But this, like soda and 
potash, he found to be a compound of a metal. This metal, 
called calcium, is very difficult to obtain, because it has so great 
an attraction for oxygen. United with oxygen, calcium forms 
lime, or what is commonly called quicklime. If water be added 
to lime, it is called slaked lime. Observe that word slaked. Peo- 
ple sometimes speak of slaking the thirst ; so, in the case of hme, 
there is a thirst, as we may say, for water, and the lime takes to 
itseM a great deal of it. But it will take only a certain amount, 
and no more. 

Lime will become slaked after a while, if it be merely exposed 
to the air ; for it has such an attraction for water, that it will 
drink in the moisture from the air. 

In making mortar, the quicklime is slaked; and so eagerly 
do the quicklime and water unite, that great commotion and 
heat are produced, as you have probably often noticed. 



IRON-RrST, POTASH, AND LIME. 77 

Ammonia and its properties. Alkalies. 

We have not yet described an interesting substance com- 
monly known as hartshorn, but called by chemists ammonia. 
It is a gas of a peculiar pungent odor with which you are prob- 
ably famihar. It is not a simple gas like oxygen, but is made 
up of two gases, nitrogen and hydrogen. It is contained in a 
substance called sal ammoniac, from which it is expelled by 
heating with lime. This gas dissolves in water, forming a very 
strong solution, which has the same odor as the gas ; it is this 
solution which is commonly called spirits of hartshorn. You 
will learn by-and-by that flesh and other parts of animals con- 
tain hydrogen and nitrogen ; when the animal matter decom- 
poses, these unite, and ammonia is formed. It is ammonia which 
smells so strong in a stable ; it also gives to guano its peculiar 
odor. 

The substances potash, soda, and ammonia are called alkalies^ 
having certain properties just the opposite of bodies called acids. 
You learned about nitric acid in Chapter lY., and you will find 
more about acids in the following chapters. These substances 
called alkalies combine with acids and form salts^ as will be ex- 
plained more fully in Chapter XYII. 

Questions. — What is said of iron ? What besides oxygen is added to iron in rusting ? 
In what condition is the water which is added ? What is said of the union of other 
metals with oxygen ? Tell about the discovery of the metal potassium. Why is it 
difficult to keep this metal ? Why is it never found alone ? In what way is it kept ? 
Describe the metal. What happens to it if it be thrown upon water ? Give the an- 
ecdote about Dr. Wollaston. W^hat is soda ? In what substance does sodium exist 
in abundance in the earth ? What is calcium ? What is quicklime ? What is slaked 
lime? What is the meaning of the word slaled? Of what is ammonia composed? 
What are its properties ? What substances are called alkalies ? 



78 METALS. IRON. 



Properties of metals. 



CHAPTER XIY. 

METALS. TRQ-N. 

Iron-eust, yon remember, is a compound of iron and oxygen, 
and is called by chemists oxide of iron to indicate its composi- 
tion. In like manner potash"^ and soda are called oxides of the 
metals potassinm and sodium respectively. Of these metals you 
learned some facts in the last chapter, and now we will describe 
some more metals of interest and importance, noticing, at the 
same time, some of their compounds. 

Most of the metals are heavy. One of them, platinum, is the 
heaviest substance in the world. But some of them, as you saw 
in the previous chapter, are so light that they will float in water. 

All of the metals are solid except mercury. This is a liquid. 
It is seen in the bulbs of thermometers. 

A metal is a simple substance, an element, and not a com- 
pound. There are forty-nine of these metallic elements, while 
there are only fourteen of all the other elements in the world. 

Metals as a class of bodies have certain properties which dis- 
tinguish them from all other substances. In masses they are 
opaque ; that is, light will not pass through them. Glass is trans- 
parentj which means you can see through it ; but you can not 
see through a piece of iron or tin. The gases are transparent, 
as you learned in Chapter II. Water is also. Ton can see sub- 

* Not the common potash of commerce, which is in reality an impure carbonate. 



METALS. IRON. 79 



Properties of metals. Uses of iron. 

stances, yon know, at the bottom of clear water in a pond or 
stream ; bnt if yon have a cnp f nil of mercnry, yon can not see 
any thing in the bottom of the cnp. 

There are some snbstances that yon can not see throngh, and 
yet light shines throngh them. They are said to be translucent. 
Metals are neither transparent nor translucent. When gold is 
made into very thin leaf by hammering, it is translncent; bnt, 
however thin it may be made, it is never transparent. 

Metals have a certain brilliancy which is called the metallic 
Instre. Some of them can be polished very highly. 

Metals can be hammered into very thin leaves, a property 
which is called malleohility^ and they may be drawn ont into 
fine wires, a property called ductility. Yon mnst not imagine 
that all metals possess these properties to an eqnal degree ; gold 
is mnch more malleable than copper, and lead is mnch less dnc- 
tile than silver, yet these properties belong to the metals taken 
as a class. If metals conld not be hammered into thin sheets or 
drawn ont into wires, they would be mnch less nsefnl than they 
now are. 

Iron is the most valuable and abundant of all the metals, and 
it is put to the greatest variety of nses. It is on account of its 
usefulness that the Creator has provided so mnch of it for man 
in every part of the world. Here are a few lines in which some 
of the many uses to which this metal is put are mentioned : 

" Iron vessels cross the ocean, Iron pipe our gas delivers, 

Iron engines give them motion ; Iron bridges span our rivers ; 

Iron needles northward veering, Iron pens are used for writing. 

Iron tillers vessels steering ; Iron ink our thoughts inditing ; 



80 METALS. IRON. 



Uses of iron. Occurrence of iron. 

Iron stoves for cooking victuals, Iron axes, knives, and chains, 

Iron ovens, pots, and kettles ; Iron augers, saws, and planes ; 

Iron horses draw our loads. Iron compounds in our blood. 

Iron rails compose our roads ; Iron particles in food ; 

Iron anchors hold in sands. Iron lightning-rods on spires. 

Iron bolts, and rods, and bands ; Iron telegraphic wires ; 

Iron houses, iron walls, , . Iron hammers, nails, and screws, 

Iron cannon, iron balls ; Iron every thing we use." 

You can think of many other uses to which, iron is put besides 
those just mentioned. We think of a 'few at this moment — 
pokers ; shovels ; sinks ; watch-springs ; plows ; hoops for casks, 
hogsheads, etc. 

Iron is never found in the earth in its metallic state, but al- 
ways combined with oxygen or some other substances, forming 
ores. These ores are of various colors and degrees of hardness ; 
some are bright -red and friable, some are yellow and earthy, 
others are black and very hard ; you would hardly think they 
looked as if they contained any iron at all, but the chemist ex- 
tracts iron from them. The ores are mixed with other sub- 
stances, chiefly with coal and limestone, and heated intensely in 
tall furnaces. Perhaps you have seen such furnaces in your 
travels. You could not very well understand the chemistry of 
the operation, and we will reserve it for the next higher book 
on chemistry. The iron thus obtained is more or less impure. 
The very best iron that can be bought has some carbon in it. 

There is a great difference between cast-iron and wrought- 
iron. Cast-iron, you know, is very brittle, while wrought-iron 
is not. The difference in composition is this : In every hundred 
pounds of cast-iron there are from three to five pounds of car- 



METALS. IRO]Sr. 81 



Different uses of wrought aud cast iron. Composition of steel. 

bon, while there is only from one quarter to one half a pound 
in every hundred pounds of wrought-iron. But this is not all 
— the structure is very different in these two kinds of iron. If 
you observe the broken edge of cast-iron, you will see that the 
iron is in little grains ; the structure, therefore, is said to be 
gramilar. But wrought-iron seems to be composed of threads 
or fibres of the metal lying along-side of each other ; so it is said 
to have 2l fibrous structure. 

These two kinds of iron aie used for different purposes. Pots 
and kettles are made of cast-iron ; but it would not do to have 
any thing made of this which is to be continually knocked 
against hard things. If, for example, horseshoes were to be 
made of cast-iron, they would be broken by the first stone upon 
which they should strike ; they are therefore made of wrought- 
iron. For the same reason, the nails with which they are fast- 
ened to the hoof are made of wrought-iron. 

Wrought-iron can be welded^ but cast-iron can not be. In 
this welding, which can be done only when the iron is red-hot, 
the hammering unites the fibres in the two pieces together. 
Tou can readily see that this can not be done with the grains of 
the cast-iron. 

Cast-iron is so brittle that it can not be hammered into sheets 
at all ; it is not, then, malleable in any degree. But wrought-iron 
is considerably so ; it is also ductile. 

Steel is a kind of iron, or rather a compound of iron and car- 
bon. In every hundred pounds of steel there are from two to 
two and a haK pounds of carbon. In respect to the amount of 
carbon in it, therefore, it is half-way between cast-iron and 

F 



82 METALS. IRON. 



The two kinds of steel. Abundance of iron. 

wrought -iron. It may be made from either cast or wrought 
iron. When it is made from cast-iron, it is done by burning out 
half of the carbon that is. in the cast-iron. When it is made 
from wrought-iron, carbon is added by heating, for several days, 
the wrought-iron with charcoal in iron boxes. 

There are two kinds of steel. One is brittle ; the other is just 
the opposite — it is very flexible. Some swords can be bent dou- 
ble without breaking, and yet will at once become straight again. 
The difference between the two kinds of steel is made in this 
way : If steel be heated, and then suddenly cooled, it will be 
hard and brittle ; if it be cooled slowly, it will be soft, and it can 
be readily hammered out like wrought-iron. All very sharp- 
cutting instruments are made of hard steel, and therefore are 
easily broken, as you may have learned some time by carelessly 
breaking your pocket-knife. 

We have spoken of the abundance of iron in the earth. Be- 
sides the ores from which iron is obtained, there is also a great 
deal of iron scattered through other substances. For example, 
almost all black and green stones get their color from an oxide 
of iron in them. The yellow stains which we sometimes see in 
marble and other stones come from an oxide of iron, which, by 
exposure to the air, has become iron-rust. Iron-rust occurs in all 
soils, but in some there is a great amount of it, giving them a 
red or yellowish-brown color. 

There is one ore of iron which is often found in the form of 
beautiful crystals ; and as it has a color somewhat like gold, it 
has often been supposed to be gold by people who do not under- 
stand such matters ; it is, therefore, called " fools' gold." Peo- 



METALS. IRON. 83 



" Fools' gold." Iron mountains of Missouri. 

pie sometimes bring samples of this ore to eliemists, supposing 
it to be a precious metal, and expecting to make a fortune, per- 
haps, from what they may gather from their land. They are 
very mnch disappointed to learn that their gold is nothing but 
iron combined with sulphur, forming a mineral nsLined pyrites. 

Iron is found in great abundance in various parts of the United 
States. You have heard, perhaps, of the two iron mountains in 
the State of Missouri. They are ninety miles south of St. Louis. 
One of them is three hundred feet high, and the other seven 
hundred. The ore of which they are mostly composed is an 
oxide of iron. Every one hundred pounds of the ore contains 
seventy pounds of iron and thirty of oxygen ; but there are some 
impurities mingled with the ore. These mountains are made up 
of lumps of all sizes, from that of a pigeon's egg to that of a large 
house. 

Questions. — What is said of the weight of the metals ? How does mercury differ 
from the other metals ? How many metals are there ? Explain what is meant by 
metals being opaque, malleable, and ductile. . What is said of the uses of iron ? In 
what state is it found? How is it freed from what it is united with? How do 
wrought-iron and cast-iron differ ? What is the structure of wrought-iron ? What 
are the different purposes to which these two kinds of iron are suited ? What is said 
of welding iron ? What is steel ? How is it made ? What are the two kinds of 
steel ? How is the difference between them made ? For what different purposes are 
they used? What is said of the presence of oxides of iron in different substances ? 
What is said of " fools' gold ?" Tell about the iron mountains of Missouri. 



84 MORE ABOUT METALS AN^D THEIR COMPOUNDS. . 

Properties of lead. Lead mines. Uses of lead. 



CHAPTEK XY. 

MORE ABOUT METALS AXD THEIR COMPOUNDS. 

Lead is an abundant and very useful metal. Its most com- 
mon ore is called galena^ and is a compound of lead and suljDhur. 
The bright shining crystals and masses of galena look very much 
like the metal itseK ; but if you tried experiments with it^ you 
would very soon learn the difference. 

Lead mines have been found in many different countries in 
all quarters of the globe. There are some very extensive ones 
in this country, especially at the "West, in Missouri, Iowa, Illi- 
nois, and on the Pacific coast. 

Lead has a bluish-gray color, and is not very lustrous unless 
recently cut; in other words, it oxidizes or tarnishes easily. 
Lead is quite easily hammered into sheets, and it melts at a low 
temperature. But it is a weak metal, for a lead wire can not 
hold up much weight. 

One of the compounds of lead with oxygen has a fine red 
color, and is largely used for making red paint. 

The uses of lead are extensive and various. Lead pipes, sheet- 
lead, lead bullets, and lead shot are familiar objects. Lead melt- 
ed with other metals forms useful mixtures, of which we shall 
tell you in the latter part of this chapter. 

Tin is a bright white metal, very soft and malleable. It does 
not tarnish easily ; that is, it does not readily rust or unite with 



MORE ABOUT METALS AND THEIR COMPOUNDS. 85 

TiD. Copper. Zinc. 

the oxygen of the air. Tin-ware, theref ore, as yon know, is easily 
kept bright. This tin-ware is not all tin. There is really more 
iron than tin in it. It is sheet-iron coated with tin. In making 
it, thin sheets of iron are dipped into melted tin. 

There are tin mines in various parts of the world. The most 
famous are those of Cornwall, in England. But little of this 
metal is found in this country. 

Copper is a metal of a red color. It does not tarnish or oxi- 
dize so easily as iron, and stands heat very well, so it is used for 
making vessels for cooking purposes. Copper is quite mallea- 
ble, so that it is readily made into sheets, such as are used in 
sheathing the bottoms of ships. It is also very ductile, and the 
wires made of it are very strong, though less so than iron wires. 
Copper is found quite pure in the earth : near Lake Superior, 
Michigan, immense masses are found, some of them weighing 
thousands of pounds. Copper is also found in many parts of 
the world combined with sulphur, with oxygen, and other sub- 
stances, and these compounds form very important ores. The 
compound with sulphur resembles " fools' gold," but has a deep- 
er yellow color. 

Zinc is a bluish -white metal which tarnishes very readily, as 
is shown by the whitish coating which gathej'S upon it. Zinc is 
brittle when cold; but if heated to a pai-ticular degree, it can 'be 
rolled into sheets. This discovery has made zinc useful for a 
great variety of purposes. Sheet-zinc is employed for covering 
roofs, lining refrigerators, sinks, etc., and for protecting the floor 
or cai-pet from the heat of stoves, besides various other purposes. 

Mercury is the only metal which is a liquid. It is a white 



86 MOEE ABOUT METALS AND THEIE COMPOUNDS. 

Discovery of mercury. Silver. Gold. 

metal, having a brilliant metallic lustre. It becomes solid in tbe 
extreme cold weather of the arctic regions. Therefore, when 
Dr. Kane and others went to those regions, they were obliged 
to use thermometers containing alcohol, which has never been 
known to become solid. 

This metal is sometimes found pnre\ It is said that the mines 
in Mexico were first discovered in this way : A hunter, as he 
was ascending a mountain, caught hold of a shrub to assist him ; 
the shrub gave way at the root, and there ran out from the 
ground a stream of mercury. It was supposed to be liquid sil- 
ver, and from its quick movement as it runs along it has re- 
ceived the name of quicksilver. 

Mercury is also found combined with sulphur, making a very 
beautiful vermilion -colored mineral called cinnabar. The most 
famous mines of mercury are in Austria, Spain, and California. 

Silver occurs in nature sometimes pure, sometimes in alloys 
or mixtures with other metals, as copper, and sometimes united 
with sulphur or some other substance. The most famous mines 
are in Mexico, Nevada, Saxony, and South America. This metal 
is very malleable and ductile. It is not so hard as copper, nor so 
soft as gold. 

Gold is rarely found in nature united with other things, as 
most metals are ; it is found either pure, or mixed with some 
other metals, forming an alloy. It is usually alloyed with silver. 
It is found in rocks, or in sands that have worn off from rocks 
by the weather, and been washed down by the rain. 

Platinum is a metal having a color like that of steel. It is 
the heaviest and most infusible of all kno^n substances. Mer- 



MOEE ABOUT METALS A^STD THEIR COMPOUNDS. 87 

The noble metals. Nature of alloys. 

cury, silver, gold, and platinuin have been called the noble met- 
als, because they are never tarnished or oxidized by the oxygen 
of the air. 

When metals are melted together, they mix and form alloys. 
Alloys are not true chemical compounds, like the oxides and the 
compounds of the metals with sulphur, to which we have alluded, 
but are mere mixtures : it is with these alloys much as with the 
liquids alcohol and water, which may be mingled in any propor- 
tion you wish. 

Pure water from every pond, river, lake, and ocean in the 
world always contains the same proportion of these two gases, 
sixteen of oxygen and two of hydrogen. ISTow, what is true of 
water is likewise true of all chemical compounds : we do not 
mean that the proportions are always two and sixteen, but that 
bodies combine in sovie definite jrroportion. Iron-rust contains, 
for example, in every 214 pounds 112 of iron, 48 of oxygen, 
and 54 of water ; laughing-gas contains in every 44 pounds 28 
of nitrogen and 16 of oxygen, etc. When you have studied 
chemistry longer, and have reached the next book of this se- 
ries, you will learn more about this subject ; meanwhile, observe 
the great difference between chemical combination and mixtures 
like alloys. 

Tou may melt together, for example, one pound of lead with 
one, two, five, ten, or fifty pounds of tin, and the two will mix, 
and, on cooling, form an alloy, the properties of which vary with 
the amount of each metal. ISTow, the case is quite different with 
bodies which unite chemically, as wlien carbon and oxygen com- 
bine to form carbonic acid, or hydrogen and oxygen combine to 



88 MORE ABOrX METALS AND THEIR COMPOUNDS. 

Difference between alloys and true chemical compounds. 

form water ; in these cases the substances unite in definite pro- 
portions, and the compound formed always contains the same 
amount of each of the bodies contained in it. Eighteen pounds 
of water are known to contain sixteen pounds of oxygen and two 
pounds of hydrogen, never more and never less of either ; thus, 
if you had a vessel holding twenty pounds of oxygen and a bag 
of two pounds of hydrogen, and should mix them and cause the 
gases to unite by setting fire to them in a proper apparatus 
(a dangerous experiment on so large a scale), so that the water 
formed could be collected and weighed, you would find only 
eighteen pounds of water 2i'xidi four pounds of oxygen remaining. 

There is another difference between alloys and true chemical 
compounds. "When two substances unite to form a compound, 
the substance which is formed is not, in its properties, between 
the two that form it ; an entirely new substance is formed, and 
generally wholly different from either of the substances of which 
it is composed. But see how it is with alloys. Brass is a mix- 
ture or alloy of copper and zinc. Its color is made lighter than 
copper by the zinc, about one quarter of it being of this metal. 
The brass is between the two metals in this respect, and also in 
other properties. 

These mixtures of metals are of very great value in the arts. 
We have just told you that brass is an alloy of copper and zinc, 
and you know how many things in common use are made of 
brass. Pewter is another alloy, made of tin, lead, and antimo- 
ny; the solder used by plumbers is an alloy of tin and lead. 
Copper and tin melted together in different proportions make 
bronze or bell-metal, the latter containing more of the tin. Ger- 



MORE ABOUT METALS AND THEIR COMPOUNDS. 89 

Uses of various alloys. Amalgams. 

man silver, as it is called, contains no silver at all ; it is an alloy 
of copper, zinc, and a metal not yet mentioned, called nickel. 

The gold and silver in common nse are not pure, but are al- 
loys. This is true both of money and of the articles for use and 
ornament made of these metals. 

When one of the metals entering into the composition of an 
alloy is mercury, the mixture is called an amalgam. One amal- 
gam you are very familiar with, though perhaps you do not 
know of what it is made ; this is the material on the back of 
looking-glasses. This is an amalgam of mercury and tin. It is 
put on in this way : Tin-foil, that is, tin-leaf, is first applied all 
over the glass ; then mercury is poured upon this, and it unites 
with the tin, making an amalgam. 

Even gold and mercury unite to form an amalgam. If you 
should try to pick up some mercury from the carpet after acci- 
dentally breaking a thermometer, and should have a gold ring 
on your finger, you would be very likely to spoil the ring. The 
gold would turn white by alloying with the mercury, and it 
would be necessary to heat the ring to redness to drive off the 
mercury again. 

Questions. — ^What is said of the occurrence and properties of lead ? What of its 
uses ? What are the qualities of tin ? What is sheet-tin made of ? What are the 
properties of copper ? Where is it found ? What is said of zinc ? What of its uses ? 
What metal is liquid at ordinary temperatures ? Relate the anecdote of its discovery. 
Where is it found ? How does silver occur ? Where is gold found ? What is said 
of platinum ? Name the noble metals. Explain the differences between alloys and 
chemical compounds. Of what is brass made ? Of what pewter ? Of what German 
silver ? What is an amalgam ? What is said of the material on the back of looking- 
glasses ? Give an illustration proving that gold and mercury form an amalgam. 



90 SULPHUR AND PHOSPHOEUS. 

Forms and occurrences of sulphur. 



CHAPTER XYI. 

SULPHUR AND PHOSPHORUS. 

Sulphur is sucli a common substance tliat we have mentioned ' 
it several times without explaining what it is. But the chemist 
has found out many interesting things about sulphur, which we 
shall now describe. 

We see sulphur ordinarily in two forms — roll brimstone and 
the flowers of sulphur. The flowers of sulphur are obtained 
by heating the sulphur so as to make it rise in vapor, the va- 
por being condensed so as to form flne powder. The roll brim- 
stone is obtained by melting the sulphur and letting it run into 
molds. 

Sulphur is very abundant in nature. It is found as sulphur, 
and sometimes in beautiful yellow crystals, in the neighborhood 
of volcanoes ; but it is most abundant in combination with other 
substances. You have learned, in the chapters on the metals, 
that they frequently occur combined with sulphur ; such com- 
pounds are called sulphides^ just as the compounds of substances 
with oxygen are called oxides. Thus the compound of sulphur 
nicknamed " fools' gold " is called in chemistry sulphide of iron. 
This mineral is an important source of sulphur. Sulphur also 
exists in the mineral called gypsum, or plaster of Paris, which 
is very common ; and, besides, sulphur enters into the compo- 
sition of many vegetables, such as onions, pease, horse-radish, 



SULPHUR AND PHOSPHORUS. 91 

Experiment with sulphur. , Sulphuric acid. 

and beans ; and of portions of animals, as in the liair, flesh, etc. 
It is the sulphur in an egg that blackens a silver spoon. 

The following is an easy experiment with sulphur: take a 
glass tube six or eight inches long and closed at one end, and 
place in it several pieces of roll sulphur the size of a 
pea. Twist a wire around the mouth of this test- 
tube, as it is called, and heat the tube in a gas-flame, 
as shown in Fig. 29. The wii*e serves as a holder, 
to prevent burning your fingers. The sulphur melts 
and sinks into the bottom of the tube ; at first it is 
thin like water, but on heating longer it becomes 
brown and thick. If you heat it a little more it be- 
comes liquid again, and on pouring this into cold 
water the sulphur hardens into a waxy mass. In this state the 
sulphur may be pulled out into strings like India rubber, but 
after a few days it becomes hard and brittle again. 

Sulphur burns in the air with a pale-blue flame, giving rise to 
a gas with a disagreeable, suffocating odor. The next time you 
light a match, look closely at the bluish flame of the sulphur, 
and smell the gas cautiously; but perhaps you have been half 
choked with the gas already. By burning sulphur in a particu- 
lar way in the presence of nitric acid and steam, and condensing 
the fumes formed, an oily corrosive liquid is obtained called sul- 
phuric acid. This acid is made on a very large scale, and is of 
great use for many purposes. When immixed with water it is 
very strong, and must be handled with great care ; a few drops 
on your clothes would eat holes through them, and a little on 
your flngers might burn them badly. 





92 SULPHUR AND PHOSPHORUS. 

Experiments with sulphuric acid. 

If sulphuric acid and water be mixed, there is produced at 
once a considerable degree of beat. This may be shown by 
some very interesting experiments. We shall mention 
two. One is represented in Fig. 30. In the vessel, a^ 
are sulphuric acid and water just poured in. In the test- 
tube, ?>, is some ether, which boils with much less heat 
than water does. Stirring this test-tube around in the 
acid and water, there is enough heat produced in a few 
moments to make the ether boil. Another experiment is this : 
Put some tow or cotton around a wine-glass, having some little 
bits of phosphorus so placed in the tow as to touch the outside 
of the glass. Pour some water into the glass, and then some 
sulphuric acid. The heat produced will set fire to the phos- 
phorus, and this in turn will set fire to the tow. 

Sulphuric acid absorbs water very eagerly : it will even ab- 
stract water from dry wood, as is proved by the following ex- 
periment : Pour some strong sulphuric acid into a glass, and dip 
into it a piece of wood ; hold it a moment in the acid, and lift it 
out, taking care not to drop any acid on the table. You will see 
that the stick is nearly black, certainly quite brown, owing to the 
charcoal or carbon contained in wood appearing on the surface. 
Sulphur combines with hydrogen, which you remember as a 
very light, combustible gas, and forms a gas of very disagreeable 
odor. It smells like spoiled eggs ; in fact, the odor of spoiled 
eggs comes from this gas itself. The coal gas burned in our 
houses for the purpose of lighting them sometimes contains con- 
siderable of this gas, and owes part of its bad odor to its presence. 
Perhaps you think we have forgotten to name the gas, but we 



SULPHUE AND PHOSPHORUS. 



93 



Sulphureted hydrogen. 



Preparation of this gas. 




only put off naming it, because the name is so long that we fear 
you will be unable to remem- 
ber it. It is commonly called 
sulphureted hydrogen^ since 
it contains sulphur and hy- 
drogen. 

The gas may be made by 
pouring some sulphuric acid, 
mixed with water, over pieces 
of sulphide of iron put into 
a bottle, like that shown in 
Fig. 31. The gas begins to 
bubble out of the liquid al- 
most immediately, without heating. The second bottle shown 
in the engraving contains some water, in which the gas dissolves. 
After some time the water refuses to dissolve any more gas, and 
then the gas passes through the curved tube ; and if a light be 
applied at the opening, the gas will catch fire and burn. Per- 
haps you wonder why we describe the manner of making a gas 
having such a very offensive odor : it is because many pretty ex- 
periments can be made with the solution of the gas in water ; 
and when you are sufficiently advanced to study chemistry in a 
laboratory, you will need to use this solution almost daily. We 
told you to use sulphide of iron to make the gas, but we do not 
mean the mineral called " fools' gold ;" this would not answer. 
An artificial sulphide of iron is used, obtained by melting sul- 
phur and iron together. 

We shall now tell you about phosphorus. This substance ex- 



94 SULPHUB AND PHOSPHORUS. 

Nature of phosphorus. Experiments with phosphorus. 

ists extensively in nature, but never by itself, like sulphur. It is 
always united with, other substances. It is commonly obtained 
from bones, in which it exists combined with lime. The bones 
of a full-grown person contain between one and two pounds of 
this inflammable substance.^ 

Phosphorus is generally sold in the form of small cylinders. 
It is white, and has a waxy look. It has so strong an affinity 
for oxygen that it is kept in water. Exposed to the air, fumes 
arise from the surface. This results from its imiting with the 
oxygen of the air. This smoking is really a slow burning ; and 
if it be in a dark place, light is given out. Phosphorus takes 
fire with so little heat that it is necessary to be very cautious in 
experimenting with it. You should always cut it under water, 
and on taking a piece out you should hold it with a pair of pliers 
or on the point of a knife. 

Some of the experiments that can be tried with phosphorus 
are pleasing, but dangerous : at least, you must not try them 
without the aid of an experienced person. 

To prepare for these, put a piece of phosphorus, of the size of 
a small pea, into a bottle containing half an ounce (a table-spoon- 
ful) of ether. Cork the bottle, and let it stand for some days, 
giving it a shake occasionally. The liquid is a solution of phos- 
phorus, and is ready for use. 

Drop some of this solution upon the hands, and rub them 
briskly together. The ether will fly off in vapor, leaving the 
phosphorus on the hands. If you do this in the evening, and 
make the room dark, your hands will be covered with light. 
The reason is, that the phosphorus unites with the oxygen of 



SIJLPHIJR AND PHOSPHOEUS. 95 

More experiments with phosphorus. Phosphoric acid. 

the air, producing combustion. If you rub your hands, the 
light will increase, because the fire is made to burn more brisk- 
ly. But what is the reason that the hands are not burned in 
doing this ? It is. because there is so little of the phosphorus 
that very little heat is produced. 

Moisten a lump of sugar with the solution of phosphorus, and 
drop it into hot water. The heat of the water sends both the 
ether and the phosphorus up to the surface, and, when they get 
there, the oxygen of the air sets fire to the phosphorus, and this 
sets fire to the ether, and off they go in a flame together. 

Pour some of the solution upon some fine blotting-paper. 
The ether evaporates, and, after it is all gone, the phosphorus 
takes fire and consumes the paper. If the blotting-paper be laid 
upon something hot, the phosphorus and ether will burn togeth- 
er, just as in the preceding experiment. 

Phosphorus can be made to burn under water ; but we advise 
you not to try the experiment, because the materials required 
are dangerous to handle. 

Phosphorus is so eager to unite with the oxygen in the air 
that a little friction produces heat enough to make it unite with 
it, and so quickly as to burn. For this reason, phosphorus is 
one of the ingredients of the substance on the ends of matches. 

When phosphorus burns, it forms a snow-like substance, which 
dissolves very readily in water, forming phosphoric acid. Sul- 
phur, you know, by a certain process, yields sulphuric acid, and 
phosphorus yields phosphoric acid. It is this substance com- 
bined with hme that makes up the chief part of bones. 

Phosphorus is very poisonous when taken into the stomach. 



96 SULPHUR AKD PHOSPHORUS. 

Poisonous properties of phosphorus. " Will-o'-the-wisp." 

It has happened several times that little children have been poi- 
soned by chewing the ends of matches. 

Phosphorus combines with hydrogen, forming a gas having 
a strong odor, resembling garlic. This gas has the very curious 
property of taking fire of itself when it mixes with air, and 
burning with a bright yellow light, while beautiful smoke-rings 
are formed if cu^cumstances are favorable. It is rather too dan- 
gerous a gas for beginners to experiment with ; but we shall tell 
you how to make it in the next book of chemistry. 

It is this gas which causes the light called " will-o'-the-wisp," 
sometimes seen at night over marshy land. Its chemical name 
is jphosphureted hydrogen. 

Questions. — Describe the nature and occurrence of sulphur. What is the chemical 
name of " fools' gold ?" What is said of there being sulphur in plants and animals ? 
Describe the melting of sulphur. Tell about sulphuric acid. What happens when 
sulphuric acid and water are mixed ? What experiments prove this ? What takes 
place when a piece of wood is dipped into. sulphuric acid? What gas gives the bad 
odor to spoiled eggs ? How can it be made ? How and where does phosphorus occur 
in nature ? What is its appearance as usually sold ? What is said of the danger of 
handling it? Describe some experiments with a solution of phosphorus in ether. 
What acid does phosphorus yield ? What is said of its poisonous qualities ? What 
peculiar property has the gaseous compound of phosphorus and hydrogen ? What is 
the " will-o'-the-wisp ?" 



SALTS, SULPHATES, ETC. 97 

ExplaiiatioD of the term "salt." Litmus. 



CHAPTEK XYII. 

SALTS, SULPHATES, ETC. 

The term salt is applied by chemists to many substances be- 
sides our common table-salt. Yon have probably heard of Ep- 
som salts^ used as a medicine, and of ^a^z^petre, nsed in the man- 
ufacture of gunpowder ; but perhaps you never thought of these 
substances as in any way related to common salt. Then we have 
Glauber's salts, salt of sorrel, salt of lemons, Eochelle salts, and 
a great many more. Now, these are old-fashioned names of 
things which have also scientific names; and since the latter 
explain something of the composition of these bodies, they are 
much to be preferred. We shall now try to explain the nature 
of the class of bodies generally called salts. 

You learned in Chapter lY. about nitric acid, and in Chap- 
ter XYL about sulphuric acid ; but we have not described a 
pretty experiment which can be made with these or any other 
acids, and which will help us to understand what follows. By 
boihng. pieces of blue cabbage, or, better, certain lichens, with 
water, a blue solution is obtained commonly called litmus. The 
smallest amount of nitric acid added to this blue solution turns 
it bright-red, and all acids act in the same manner. A few drops 
of the strong blue solution will color a tumblerful of water 
light-blue, and a single drop of the stronger acids will change 
this color to red. Now, this red solution may be changed back 

G 



98 SALTS, SULPHATES, ETC. 

Use of litmus solution. Formation of salts. 

to blue again by adding soda, potash, ammonia, or any other 
alkaline substance. This change from blue to red, and back 
again, may be made many times in the same solution, the acid 
turning it red, and the alkali blue. 

If you prepare two solutions, one of potash, and the other of 
nitric acid, and add a little litmus to each, and then mix the so- 
lutions carefully, you will find that it is possible to reach a point 
when a single drop of either the acid or the alkaline solution 
will change the color from red to blue, or from blue to red. 
The acid, as we say, neutralizes the alkali. 

If you pour this mixture into a proper dish and boil out most 
of the water, and let the rest cool slowly, you will obtain crys- 
tals of a substance made up of nitric acid and potash, called by 
chemists nitrate of potash^ and which is commonly known as 
saltpetre. This substance, on drying, will burn and sparkle 
in a lively manner if thrown on red-hot coals, a property which 
is possessed by neither the nitric acid nor the potash alone ; so 
we have here another example of chemical union, about which 
you learned in Chapter XY. 

The saltpetre, being made from nitric acid and potash, is called 
nitrate of potash. Had we used sulphuric acid in the place of 
nitric acid for the above experiment, we should have obtained 
sulphate of potash ; and, on the other hand, had we used soda 
instead of potash, we should have nitrate or sulphate of soda. 

Substances which are neither acid nor alkaline, and which yet 
contain the main ingredients of both acids and alkalies, like the 
sulphate of potash, are called salts. You will find, on studying 
a more advanced book on chemistry, that this definition is not 



SALTS, SULPHATES, ETC. 99 

Manuer of Darning salts. Sulphate of lime. 

strictly correct, for some salts are very acid ; but the ordinary 
salts, of which, we shall speak, are chiefly included in it. What 
we want you to particularly notice is the manner in which these 
substances are named : the syllable ate is added to the name of 
the acid, and the name of the hase^ as it is called, is written 
after it or just before it. Thus, soda and nitric acid unite to 
form nitrate of soda, or sodium nitrate ; potash and phosphoric 
acid form potassium phosphate ; iron and sulphuric acid, iron 
sulphate ; and so on. 

In describing the manner in which nitric acid and potash nevr 
tralize each other, the two solutions were mixed in the presence 
of litmus merely for the purpose of ascertaining when enough 
of each had been added : you must not imagine that all salts are 
prepared in this way. Many substances called by the chemist 
salts occur ready formed in nature, and we shall tell you about 
some of these in this and the following chapters. 

One of the most abundant of the salts of sulphuric acid is the 
sulphate of lime. This is sometimes called gypsum, and some- 
times plaster of Paris. It received this latter name because 
there are immense quantities of it near Paris, and it was first 
used in that city as a plaster. 

Sulphate of lime is a very mild substance, and yet it is made 
of two very active substances. Lime is quite caustic, and sul- 
phuric acid is one of the most corrosive substances in the world. 
Mix lime, as the gardener sometimes* does, with weeds, and it 
wiU rot them quickly by its caustic power ; and if you drop 
Sulphuric acid upon your skin, it will eat it. But let the sul- 
phuric acid and the lime unite, and you have a substance that 



100 SALTS, SULPHATES, ETC. 

Forms of gypsum. How gypsum unites with water. 

yon can handle, and, when powdered and wet, yon can mold it 
with yonr fingers. Here we have one of the most striking illus- 
trations of the fact so frequently seen, that a substance may be 
wholly unlike the ingredients that compose it. 

Some of the forms in which gypsum is found in nature are 
very beautiful. The alabaster, which is cut into vases and other 
oi^iaments, is one of them. Sometimes this mineral is arranged 
in delicate white fibres, and then it is called satin spar. It is 
well named, for it is as elegant as satin. Sometimes it is in 
very thin leaves, laid closely together, and at the same time it is 
as clear as water. It is then said to h^ foliated^ a word which 
comes from the Latin word that means leaf. The common word 
foliage comes from the same source. 

Gypsum is used in powder for a variety of purposes. In using 
it, the fact that one -fifth of the substance is water is of great 
service. We will tell you how this is. Suppose that you wish 
to make a plaster cast. You subject the powdered gypsum to 
considerable heat to drive off this water in it. Then you wet it 
so as to make a paste of it. With this paste you mold your 
figure. Then you let it stand till it becomes dry and hard. 
Observe what happens. Does the plaster merely dry as a wet 
cloth does ? that is, does the water which has been mingled with 
it pass off into the air ? Some of it does ; but a large part of it 
becomes a part of the plaster. The gypsum really takes to it- 
self, and makes a part of its solid self, exactly as much water as 
it lost when it was heated. It is precisely as the quicklime 
takes up water, as stated on page 76. 

You can take very pretty copies of coins or medals with this 



SALTS, SULPHATES, ETC. 101 

Uses of plaster of Paris. Epsom salts. Other sulphates. 

plaster. You can buy a little of it from whicli the water lias 
been expelled. Moisten some of it, and put it into a small round 
paper box. Large-sized pill-boxes will answer. Press now a 
coin upon the surface of the plaster. When the plaster is dry 
and hard, take the coin off, and you will see a good impression 
of it in the plaster. To prevent the coin from sticking to the 
plaster, oil it very slightly. 

The hard-finish which is put upon our walls is made of this 
plaster from which the water has been driven off. First the 
wall is plastered with common lime mortar. Then some of the 
powdered gypsum is stirred up in water, so as to make a thin 
paste, and this is nicely spread upon the wall and left to harden. 

Sulphuric acid united with soda forms a sulphate of soda, or 
Glauber's salts, as it is c'alled. This salt forms large white crys- 
tals. With magnesia, sulphuric acid forms sulphate of magne- 
sia, which is called Epsom salts. This is in the form of very 
white small crystals. It is really a very pretty substance, but it 
has a bitter, disagreeable taste, as you may well know if you 
have ever taken any of it as a medicine. Both of these salts 
are called neutral salts, for the acid properties of the sulphuric 
acid are wholly neutralized in them. 

You can try a pretty experiment with sulphate of copper. 
Dissolve some of this salt in a little water. Hold the blade 
of your knife in the solution for a few minutes. On taking it 
out, you will find it covered with a red coat, which is metallic 
copper. This is because the copper leaves the sulphuric acid 
and takes the place of the iron, the latter dissolving in the 
acid. 



102 SALTS, SULPHATES, ETC. 

Gunpowder. Gases formed by its explosion. 

l^itrate of potash, formed by the nnion of nitric acid and pot- 
ash, is commonly called either nitre or saltpetre. It is chiefly 
interesting as being one of the ingredients of gunpowder. This 
article is made of three things: nitre, charcoal, and snlphnr. 
They are very carefully mixed. When fire is touched to this 
mixture, it readily burns, and a great quantity of gas is suddenly 
produced. It is this gas, striving to get room for itself, that 
drives the ball out of the gun or cannon, as has been explained 
in the Third Part of the Child's Book of N"ature. 

But how is this gas produced? The nitre contains nitrogen 
gas, and a great deal of oxygen gas. When the powder burns, 
the latter quickly unites with the carbon, forming a great amount 
of carbonic acid gas ; and at the same time the nitrogen gas is 
set free. Carbonic acid gas and nitrogen are, then, the chief 
gases set free in firing gunpowder, and produce the explosion. 

How great is the change in this case ! From a small quan- 
tity of powder comes out, all at once, a very large bulk of 
gases. We say comes out, for the gases in that powder were 
locked up, and squeezed, as we may say, into small quarters. 

Questions. — Name some substances called salts. Describe the experiment with a 
solution of litmus. Explain how potash and nitric acid neutralize each other. What 
salt is obtained by evaporation of the mixture named ? Explain the general manner 
of naming salts. What salt is formed by soda and sulphuric acid ? What by iron 
and nitric acid ? What is gypsum ? How does it occur in nature ? What is satin 
spar ? Of what use is gypsum ? Tell how models of medals and coins are made. 
What is the substance known as Glauber's salts ? Describe Epsom salts. Show how 
copper will coat a steel blade of a knife. Of what is gunpowder made ? What gases 
are set free when it is burned ? Why does it explode ? 



LIMESTONE, SHELLS, AND CORALS. 103 

Composition of marble. Varieties of limestone. 



CHAPTEE XYIII. 

LIMESTONE, SHELLS, AND COEALS. 

You will perhaps be surprised to learn that chemists call mar- 
ble a salt. It certainly has no taste like salt, for it is but little 
soluble in water ; but since it contains a base and an acid, it is 
classed among the substances called salts. You learned in Chap- 
ter YI. that chalk and marble are made up of lime and carbonic 
acid ; and you remember that the carbonic acid gas could be set 
free by pouring over the pieces of marble an acid called hydro- 
chloric. Since marble contains the above-named ingredients, its 
chemical name is carbonate of lime. You would hardly suppose 
that such hard substances as marble and limestone could be com- 
posed of exactly the same things as the soft, crumbling chalk ; 
but we have many examples like this. 

Limestone and marble are merely different varieties of car- 
bonate of lime ; they vary in their granular structure, and some- 
times the former contains a little carbonate of magnesia, but 
this is not essential. Whole mountains are made up of lime- 
stone, and in some parts of the country no other rock is found 
for miles around. So you see carbonate of lime is a very abun- 
dant substance. Sometimes the limestone appears in beautiful 
crystals, transparent and shining ; one variety is called dog-tooth 
spar^ from a fancied resemblance. Perhaps you have seen speci- 
mens of this mineral. 



104: LIMESTONE, SHELLS, AND COEALS. 

FormatioD of stalactites and stalagmites in caves. 

Carbonate of lime does not readily dissolve in water; but 
water will dissolve some, especially if there be carbonic acid gas 
in the water. The water that comes from some springs has, for 
this reason, considerable of this salt in it, and some of it is depos- 
ited upon stones and sticks above the spring, crusting them over. 
In some caves in limestone regions we have beautiful displays 
of the formation of limestone from water in which this salt is 
dissolved. As the water drips from any spot in the roof of the 
cave, some of the carbonate of lime stays upon the roof. Then, 
as more and more adheres, a projection is formed pointing, do^m- 
ward, very much like an icicle as water drips in cold weather from 
the eaves of a house. At the same time, there is formed under- 
neath, on the floor of the cave, a little hillock of the limestone 
from the water that drops there. That which forms above is 
called a stalactite, and that below a stalagmite. 

Sometimes, when there are many of these stalactites and sta- 
lagmites, and they have been forming for a long time so as to 
reach a great size, they present a splendid appearance. In Fig. 
32, you have a picture of a celebrated grotto in Cuba. Here 
the stalactites and stalagmites present every variety of form and 
arrangement, and, lighted up with torches, the place looks like a 
scene of enchantment. 

When limestone is heated in a furnace, the carbonic acid flies 
off and quicklime remains. Quicklime, you remember, is really 
an oxide of a metal called calcium. 

The shells you pick up. on the sea-shore are made of carbonate 
of lime. All oyster-shells are made of this substance. The lime 
which is used for making mortar and for other purposes is often 



LIMESTONE, SHELLS, AND COEALS. 



105 



Nature of oyster-shells. 



Source of the carbonate of lime. 



Fig. 32. 

iita^iiiil 




obtained by burning oyster-shells, just as we obtain it from lime- 
stone. 

Whence comes all this carbonate of lime of which the shells 
are made ? It is in the water, dissolved in it as the salt is. But 
how does it get into the w^ater ? It comes from the earth and 
the rocks of limestone. It is washed along with the water as it 



106 

How an oyster's shell is made. How coral animals grow. 

runs in brooks and rivers, and at lengtii conies to the sea. Here 
there is more of it in the water than anywhere else. 

But how is this carbonate of lime made into shells ? Does it 
gather from the water on the outside of the animals that lijre in 
them ? Does the oyster, for example, merely lie still, and let 
the shell grow on him by having the carbonate of lime settle 
upon him by little and little from the water, as it encrusts a 
stone or a stick in a spring ? 'Noy this is not the way. All that 
big rough shell has been swallowed by the oyster, and has been 
in its body. Only a little at a time was swallowed, dissolved in 
the sea-water in which it lives ; but that little was used in build- 
ing the shell-house. 

Look at an oyster-shell carefully. There are different layers. 
The outside layer is smaller than the next one, and this is smaller 
than the next, and so on ; and the one next to the oyster is the 
largest. The outside layer was made when the oyster was very 
small — a baby oyster, as we may say. Then, as he grew a little 
larger, another layer was formed from the carbonate of lime as 
it oozed out from his body, and so on to the last and largest. 

All shells are not made exactly after the plan of the oyster- 
shell ; but it is as true of them all as it is of the oyster-shell, that 
every particle of them has been swallowed in the water drunk 
by the animals that lived in them. 

There is one class of animals that live in the sea which make 
a singular use of the carbonate of lime they continually swal- 
low. We mean the coral animals, as they are called. These lit- 
tle animals always stay exactly where they are born. They are 
fixed to a strong foundation. That foundation is their skeleton, 



LIMESTONE, SHELLS, AND CORALS. 107 

Coral animals reef-builders. All Florida made by them. 

formed from the carbonate of lime which they have swallowed. 
This skeleton extends np into the animal's body. The animal 
is all the time growing upward in the water, and adds continu- 
ally to the top of its skeleton. In the mean time, the lower part 
of its body is always dying. It dies below while it grows above. 

Tou see what the effect of all this is. The animal builds a 
column of carbonate of lime, he being all the time at the top of 
it, sitting on it like a well-fitted cap. 

But these animals always live and work in companies. If a 
great many of them, then, build their columns side by side, 
a great deal of building will be done, though each does but lit- 
tle. Whole islands have been built in this way. Long ranges 
of coast, sometimes for hundreds of miles, have been lined 
with reefs built up by these little animals. Some of the tiny 
builders that do such work are no larger than the head of a pin. 
ITearly all the foundation of Florida has been gathered from 
the water by these little reef -builders. 

"We wiU show you how this building was done. All along 
the coast of Florida, a little way out from the main-land, there 
are islands called Tceys. These have been built up by the coral 
animals. They began their work down deep at the bottom of 
the sea, and worked along upward till they reached the surface. 
Then their work was done, for they can not work out of water ; 
and their work being done, they died. 

But something more needs to be done to make these coral 
reefs fit to live upon, for they are merely plains, as we may call 
them, of carbonate of lime, which reach just to the surface of 
the water. After a while they do become real islands, and things 



108 LIMESTONE, SHELLS, AND COKALS. 

Formation of islands from coral reefs. Egg-shells. 

grow upon them, and people live there. The waves, dashing 
over the reefs, break them up somewhat, and the pieces are 
washed up toward the middle of the reef. At the same time, 
the various things floating about in the sea collect there, and the 
sea-weed is thrown up upon the heaps in considerable quantities 
by the waves. All this gradually forms a soil upon the reef, 
and makes it a real island. Seeds are dropped there by birds, 
or are carried there in the water, and are washed up on to the 
land. Grass, flowers, shrubs, and trees soon grow there, and 
then man comes and plants such things as he wishes to have 
grow, and builds his habitation. 

Egg-shells are made of carbonate of lime ; but hens sometimes 
lay eggs with no shells on them. Why is this ? It is because 
the hens have not swallowed enough carbonate of lime. They 
swallow it mingled w^ith their food, the dust of it being scatter- 
ed about from broken oyster-shells, chalk, etc. As the canary- 
bird pecks away at the cuttle-fish bone that hangs in its cage, 
some of it becomes mingled with its food, and, being swallowed, 
is used in making the shells of the eggs that the bird lays. 

Qaestiom. — ^What is marble made of? Why is it called a salt? What is the 
difference between marble and limestone? What happens when water containing 
dissolved carbonate of lime drips from the roof of a cave ? What are stalactites ? 
How is quicklime made ? Of what are shells made ? How is lime obtained from 
shells ? Whence does the carbonate of lime in the water come ? How is it made 
into shells ? Describe the manner in which the shell of the oyster is formed. What 
is said of the formation of shells generally ? Describe the manner of the growth 
of the coral animal. What is the result of this process ? What is the result if many 
of them are along-side of each other ? What is said of th'e extent of their building ? 
What is said about Florida ? When the coral animals have finished their work, how 



PEARLASH AND OTHER CAEBONATES. 109 

Pearlash, and the method of its maunfacture. 



CHAPTEE XIX. 

PEARLASH AND OTHER CARBONATES. 

There are a great many carbonates besides carbonate of lime 
or limestone, and some of these we shall now describe. 

Carbonate of potash, commonly called pearlash, is a very dif- 
ferent substance from carbonate of lime. It dissolves in water 
very readily. It is obtained from the ashes of plants ; the plants 
taking it up from the soil. Not many years ago it was common 
for every family in the country to have what was called a leach- 
tnb. In this were put the wood -ashes. Water being poured 
over the ashes, there ran out, from a hole below, a liquid called 
lye. This contained the carbonate of potash and caustic potash 
together in solution. There is caustic potash as well as the car- 
bonate, because the ashes contain lime. The explanation is this : 
Lime, having a greater affinity for carbonic acid than pearlash, 
takes away this gas from some of the carbonate, thus changing 
it into caustic potash. The quantity of the caustic potash in 
the lye is increased by putting some lime into the bottom of the 
leach-tub. The efiEect of this is to change much more of the 
carbonate of potash into caustic potash than would be changed 
by the little lime in the ashes. Leach-tubs are now much less 
used by families, as pearlash is made from ashes mostly in large 
establishments. ^ 

This mixture of carbonate of potash and caustic potash is 



110 PEAELASH AND OTHER CAEBONATES. 

A contrast. An easy experiment. • 

called simply potash by most people, but this is not strictly 
correct, for this name belongs properly only to caustic potash.* 
We have told you that if carbonate of lime be heated strongly, 
the carbonic acid will be driven off. Carbonate of potash is very 
different in this respect. The hottest fire can not drive off the 
carbonic acid from it. If heat could do it, we should not have 
any carbonate of potash in ashes, but caustic potash, the car- 
bonic acid having been carried off into the air. 

Here is a little experiment that you can try with carbonate of 
Fig. 33. potash. Drop a tea -spoonful of this salt into 

a tumbler half full of vinegar. There will be 
^!|^ a brisk effervescence, a gas escaping from the 
^^^'^'^L liquid. ITow lower a burning taper into the 
-^ tumbler, as represented in Fig. 33. The flame 
Jl will be extinguished. "Why? Because the gas 
111 ml I which rises and fills the tumbler is carbonic acid. 

B^iH The acetic acid in the vinegar takes the potash 

^^^^P away from the carbonic acid, and a salt is form- 

ed by the union of the acetic acid and the potash. 
You can tell what the name of it is by observing what we have 
told you about the names of salts on page 98. 

If you dissolve some potash in water, and then boil in the so- 
lution some dirty greasy rags, the solution wiU become very dark 
and dirty, but the rags will be white and clean. The potash 
combines with some of the ingredients of the grease, and the 
new compound dissolves in the water ; but in uniting, the dirt 

*jiCaustic potash is one of a class of bodies called hydrates, concerning which de- 
tails will be found in Hooker's Chemistry, Science for the School and Family, Part II. 



PEAELASH AND OTHER CAEB0NATE8. Ill 

Operations of soap explained. Saleratus. Carbonate of soda. 

has been taken out of the cloth^ with the grease, by the potash. 
This explains the use of soap in washing. In making common 
soft soap the potash is united with grease or fat and water, but 
there is not so much grease as to prevent the potash from unit- 
ing with more grease. The potash alone would be a very harsh 
material to wash with, but by mixing it with grease and water 
we make a very smooth article that we can use easily. In wash- 
ing clothes, the potash in the soap takes out all the oily matter 
which has come from the perspiration, and with it the dirt ; and 
if there be dirt alone without any oily matter, the soap readily 
mingles with it, so that the water can take it out better than it 
can without the soap. 

Water and oil, you know, will not mix, no matter how much 
or how long you may shake them together ; when you stop shak- 
ing them in a vessel, they gradually take their places, the water 
sinking and the oil rising. But if you pour in a solution of 
pearlash or potash, and shake again, it acts upon the oil, forming 
with it soap, which then dissolves in the water. 

Besides the ordinary carbonate of potash, there is another 
commonly called the bicarbonate, or saleratus. This is often 
used for raising bread and cake, some acid being added to drive 
out the carbonic acid gas ; and this gas set free, everywhere in 
the dough makes little spaces or cells, swelhng it up. Sour milk 
is often used, since it contains enough acid to decompose the 
bicarbonate of potash. 

Carbonate of soda is a very important and useful substance. 
It was formerly obtained by leaching the ashes of certain sea- 
weeds, but is now made more cheaply from common salt. It 



112 PEAELASH AND OTHER CAEBONATES. 

Carbonate of magnesia. White lead. Lead poisoning. 

forms transparent crystals wliich. crumble to a wliite powder. 
When dissolved in water, it forms an alkaline solution, soapy to 
the touch, and which turns reddened litmus solution blue. Its 
uses are so numerous that we can not tell you half of them : 
for washing greasy things it is stronger than soap ; hard soap it- 
self is largely made from it ; and it is used in making glass, as 
will be shown in the next chapter. 

One sort of carbonate of soda, commonly called the licarbO' 
nate^ is used for making home-made soda-water. The manner 
of using the w^hite powders sold by druggists for this purpose 
has been already explained on page 38, but you are now better 
prepared to understand the chemistry of the operation. When 
the solution of bicarbonate of soda is mixed with the solution 
of tartaric acid, an exchange of acids ensues; the carbonic acid 
leaving the soda and going off with effervescence, while the 
tartaric acid combines with the soda, forming tartrate of soda. 
This remains in solution, and has no injurious effect on persons 
drinking the soda-water. 

There is a carbonate of magnesia. This is the common mag- 
nesia used in medicine. If this be heated very thoroughly, the 
carbonic acid will be driven off, just as it can be driven off from 
carbonate of lime or chalk. This changes the carbonate into an 
oxide of the metal magnesium. This oxide is the so-called cal- 
cined magnesia^ which very probably you have taken as medicine. 

The carbonate of lead is the " white lead," so called, used so 
much in painting. This is a very poisonous salt. It is often 
formed in the lead pipes used for conveying water ; and as it is 
somewhat soluble, it is carried into the system of those who 



TEAELASH AND OTHER CARBONATES. 113 

Action of water on lead pipe. Smelling-salts. 

drink the water, and gradually produces painful disease, which 
sometimes ends in death. What appears at first thought singu- 
lar is, that the purer the water, generally the more apt is this 
salt to. form. This is, however, easily explained. When the 
water is not pure it commonly has some substances in it which 
act on the lead in such a way as to form a thin coat which is not 
soluble in the water. This prevents the oxygen and carbonic 
acid in the water from acting upon the lead. Fortunately, the 
substances dissolved in water are usually such as to make the 
fixed coating, and therefore most waters can be safely carried 
through lead pipes, though tin-lined lead pipes are better. 

Smelling-salts, with which you may be familiar, is the com- 
mon name given to another carbonate, carbonate of ammonia. 
This substance is prepared on a large scale by heating in closed 
iron vessels bones, hartshorn, and other animal matters, and then 
purifying it by sublimation. It is used in medicine, and in the 
chemical laboratory. 

Questions. — How is pearlash made ? For what is lime added ? How does vinegar 
act on carbonate of potash ? Why does potash clean greasy articles ? Why does it 
make oil and water mix ? What is saleratus ? How is carbonate of soda made ? Of 
what use is it ? What is said of the bicarbonate of soda ? Explain the chemistry 
of making soda - water. What salt remains in solution ? What of the carbonate 
of magnesia ? Of carbonate of lead ? Explain the danger of using lead pipes for 
conveying drinking-water. What are smelling-salts ? Of what are they made ? 

H 



114 GLASS AND EARTHENWARE. 

Nature of silica. Use of saud in mortar. 



CHAPTER XX. 

GLASS AND EAETHENWAEE. 

The beantiful, white, shining particles of sand seen on the 
sea-shore or elsewhere, the brown flint, the clear rock-crystal 
which often occurs in symmetrical forms, and the various sorts 
of agates, are all made of one and the same thing, called by 
chemists silica. Silica is the oxygen compound, or oxide, of a 
substance called silicon, which is, however, never found as such 
in nature. Is not this curious ? Silica, so abundant in sand and 
rocks, and yet silicon itself never occurring? But this is not 
the first case we have met of a similar nature. Lime, you re- 
member, is an oxide of the metal calcium, and the latter is never 
found in nature, though limestone is so common. 

Silicon is not a metal, but a substance somewhat resembling 
carbon, and the oxide silica is nearly related to the oxide of car- 
bon you have learned to call carbonic acid ; consequently, silica 
is often called silicic acid^ though there are scientific reasons for 
disapproving of this name. Silicic acid unites with potash and 
soda and lime, forming bodies called silicates^ just as carbonic 
acid forms carbonates. The silicates of lime and soda consti- 
tute glass. 

You know that in making mortar we put in sand with the 
lime. This gives firmness to the mortar. Lime and water would 
not' answer alone. But the sand has another effect : the longer 



GLASS AND EARTHENWARE. 115 

Composition of glass. Discovery of glass. 

the mortar or plastering remains, the harder does it become ; and 
very old plastering, as we see in tearing down old houses, is very- 
hard indeed. This is because the silicic acid in the sand gradu- 
ally unites with the lime ; so that, in the course of years, there 
comes to be considerable silicate of lime in the plastering. 

Glass is not one silicate alone, commonly, but a compound 
containing two or more silicates. Thus, common window-glass 
is a silicate of both lime and soda together. To make it there 
are melted together, with a very hot fire, fine nice sand, old 
glass, limestone, and soda. Limestone, you know, is carbonate 
of lime. The heat drives off the carbonic acid, and the lime, 
released from this acid, unites with the silicic acid of the sand, 
forming silicate of lime. At the same time the soda combines 
with this acid, making silicate of soda, and the two silicates, unit- 
ing in one, form a silicate of lime and soda. The different kinds 
of glass are, you know, insoluble ; but there is a way of making 
glass that will dissolve, and it is used as a fire-proof varnish. 

The various colors of glass are made by various oxides of 
metals mingled with the melted glass — oxides of iron, copper, 
manganese, etc. 

It is stated in a very old book that the making of glass was 
discovered by accident. Some people going on a voyage were 
driven on shore at a very sandy place. There was a great deal 
of sea-weed, which had been thrown up upon the shore, and had 
dried in the sun. With this they made a fire on the sand, and 
it was observed that there was mingled with the ashes some 
substance that was hard, and had a glassy appearance : it was 
really glass. You see the explanation of this. The ashes fur- 



116 GLASS A^D EAETHENWAEE. 

Composition of clay. Bricks. Glaziug. 

nished the alkali and the sand the silica to make the silicate, 
that is, the glass. If this be all true, it is one of many ex- 
amples which we have illustrating the fact that a vast deal 
can be often learned by thinking about the common things 
that we happen to see. A glassy appearance in the ashes of 
sea -weed most people would not spend a thought upon; but 
an observer inquires what causes this appearance, and, in pursu- 
ing the inquiry, perhaps makes a valuable discovery. Be not, 
then, mere sight - seers as you go through the world, but ob- 
servers ; and observe little things as well as great. 

All earthenware contains clay. It is quite pure in porcelain, 
and very impure in common flower -pots, and especially in 
bricks ; that is, it is mingled with other things, sand, etc. 

Clay, like glass, is a silicate. Perfectly pure clay is a silicate 
of alumina. But all clay, as we find it, contains more or less of 
other silicates — of lime, of potash, etc. 

The brownish-red color of bricks and common flower-pots is 
owing to the rust of iron in the clay. 

Bricks, you know, are quite porous, and consequently will ab- 
sorb water. This is also the case with common flower-pots. This 
porousness will do us no harm in this case, but generally it is 
necessary to have earthenware so made that no fluid can escape 
through its pores. It would not answer, for example, to keep 
preserves in jars of porous earthenware. The watery part would 
gradually escape through the pores, and the preserves would be- 
come dry. 

The difficulty is remedied in two ways. One is to glaze the 
surface of the earthenware; that is, a glass surface is made. 



GLASS AND EAItTHENWAEE. 117 

Glazing earthenware. Silica in plants. 

This is done in various ways. One method you will be inter- 
ested in, because you can understand the chemistry of it. The 
fumes of common salt are made to envelop the articles of earth- 
enware when they are very hot. Now, salt is composed of a gas 
(chlorine) and the metal sodium, as we shall explain more particu- 
larly in the next chapter. You learned something about sodium 
in Chapter XIII. In the glazing, the chlorine leaves the sodium 
to unite with some of the iron in the earthenware. Then the 
sodium, thus left by the chlorine, unites with the silica in the 
earthenware to form a silicate of soda, thus making a soda glass, 
as we may call it. So you have a coating of this glass all over 
the articles. 

Another mode of making earthenware impervious to water is 
to make the ware partly earthen and partly glass. The ingredi- 
ents are so selected that the silicates of lime, potash, etc., of 
which glass is made, are thoroughly united with the silicate of 
alumina, or clay. This stops up all the pores, and does not 
merely shut those which are outside, as the glazing does. 

Silica is a very important part of some plants. It is in the 
stalks of all grass, giving them such firmness that they can stand 
up. It is also in the stalks of all grain. It is to these and some 
other plants very much what bones are to animals. In some 
plants there is so much silica that they are used for scouring. 

But how does this silica get into plants ? Even if you make 
it very fine indeed, and put it into water, none of it will dis- 
solve. It seems strange, then, that any of it should go with the 
sap up into any plant. To do this, it must be made very fine, 
much finer than we can make it by pounding and grinding ; and 



118 GLASS AND EARTHENWARE. 

Silica in plants. Nature never makes mistakes. 

this is done in some way, we know not how, about the roots of 
plants. But this is not enough; it must be changed so as to 
make it dissolve in water, or it will not go up in the sap ; and 
this is done by means of the potash that is in the ground with 
the silica. But little is required, and that little is furnished dis- 
solved in the sap. And then, as it goes up, it is lodged just 
where it is wanted in the stalk. None of it gets by mistake into 
the kernels of the grains. If it did so, our flour would be grit- 
ty, and our teeth would soon be worn out. 

Questions. — Of what is sand composed ? What other substances are made of sili- 
ca ? What is silicon ? With what does it combine ? Tell about silica in mortar. 
What are the salts made by silica called ? What is common window-glass ? Tell 
how it is made. What is said of soluble glass ? How are the various colors of glass 
produced ? Relate the anecdote about the discovery of the way to make glass. Of 
what is earthenware made ? What is the composition of pure clay ? What else is 
there commonly with it ? What is the cause of the brownish-red color of flower-pots 
and bricks ? What is said about their porousness ? What is glazing, and what is the 
use of it ? Describe and explain glazing with salt. Describe another way of making 
earthenware impervious to water. What is said of silica in plants? How does it 
get into them ? 



CHLORINE AND COIVIMON SALT. 119 

Composition of common salt. Properties of chlorine. 



CHAPTEE XXI. 

CHLORDTE AND COMMON SALT. 

The salts noticed in tlie previous chapters contain oxygen; 
bnt there are some salts in which there is no oxygen. They are 
formed by the union of certain simple substances with a metal. 
Common salt is one of these salts. In this substance the metal 
sodium is united with a very singular gas called chlorine, and 
so the chemists call it the chloride of sodium. 

You remember that all the compounds of the gas oxygen 
formed with metals are called oxides, so all the compounds of 
this gas chlorine are called chlorides. 

Before we tell you particularly about salt, we shall speak of the 
gas chlorine. It is one of the gases that have color. Its color 
is a greenish-yellow. It has a powerful and very peculiar odor, 
and, if breathed, is very injurious. Even when diluted with 
considerable air, it is very suffocating. If you should breathe 
it without any air mixed with it, you would die. 

Chlorine is of great use in purifying foul air. You, perhaps, 
have seen chloride of lime exposed in rooms where there is sick- 
ness of such a kind as to cause bad odors. It is the chlorine 
arising from this that purifies the air. The little chlorine that 
escapes into the air in this case, although you smell it quite 
strongly, does not interfere with your breathing, for it is very 
largely diluted with air. 



120 CHLOEINE AND COMMON SALT. 

Chlorine a purifier of air. Bleaching with chlorine. 

The odor of this gas is so peculiar that if yon have ever 
smelled it once, yon always know it afterward. Yon smell it in 
mannfaetories where there is bleaching of cloth going on. Yon 
smell it, therefore, in paper-mills, for the rags ont of which the 
paper is made are bleached by it. 

We will tell yon abont this bleaching. If yon pnt a rag of 
calico into a jar of chlorine gas, no effect will be prodnced on 
its colors ; bnt moisten the rag before it is pnt in, and the colors 
will be taken ont by the chlorine at once. Chlorine mnst have 
water present, or it will not bleach. 

Chlorine gas will dissolve in water, and the solntion is very 
convenient to nse in bleaching. A calico rag dipped into it is 
very soon made white. It will take ont ink-spots also. It has 
no effect npon printers' ink, however, for the latter contains 
lamp-black. 

Yon see the great nsefnlness of chlorine in making paper. 
White paper can be made ont of rags of all colors, becanse the 
colors can be removed by the chlorine. Yon see, too, its nse- 
fnlness in whitening cloth. The old method of doing this was 
very slow. It was to spread cloth ont npon grass for the snn, 
and rain, and dew to whiten. This, called grass-lleaching^ took 
weeks ; bnt, with the quicTc lleaching by chlorine, the same thing 
is done in a few honrs. Some care is reqnired not to have the 
chlorine water too strong, and to get all the chlorine ont of the 
cloth after the bleaching is done. If this care be not exercised 
the cloth will lose some of its strength, some of the snbstance of 
the cloth being eaten ont, as well as the coloring matter. 

A convenient way of making chlorine withont mnch appara- 



CHLOEINE AND COMMON SALT. 



121 



Modes of obtaining chlorine. 



Fig. 34. 



tiis is the following : Pour into a pint bottle two table-spoonfuls 
of dilute sulphuric acid, and add a little more than the same 
quantity of chloride of hme, or bleaching powder. Add the 
powder gradually, covering the bottle with a slip of 
glass each time after dropping some in, as repre- 
sented in Fig. 34. Chlorine made in this way, though 
not pure, will answer for many of the experiments. 

The explanatTon is this : The sulphuric acid unites 
with the lime, and the chlorine, being thus sepa- 
rated, rises and fills the bottle. 

Another method is to put some black oxide of ~^"^"^ 
manganese into a flask, and pour in enough hydrochloric acid to 
cover it, as seen in Fig. 35. Gentle heat must be applied, and 




Fig. 35. the gas will pass over into the 

bottle which is placed to receive 
it. Tou observe that the tube 
reaches to the bottom of the 
bottle. This is to have the 
chlorine gas push up the air 
which is in the bottle, which it 
readily does, taking its place in 
the bottle. It is two and a haK 
times as heavy as air, and so has 
no disposition to escape upward. 
Tou can tell when the bottle is full by the color. When it is 
full, slip it out from under the tube, cork it, and place the tube 
in another bottle. 

In this method of obtaining chlorine the gas comes from the 





122 CHLOEINE AND COMMON SALT. 

Chlorine supports combustion. Hydrochloric acid. 

hydrochloric acid, an acid of which we shall tell you more pres- 
ently. It is the same acid we used in making carbonic acid 
from marble, as explained in Chapter YI. 

Although chlorine gas is so destructive to life when breathed, 
it supports combustion. If a taper (Fig. 36) be intro- 
^^* * duced into a bottle of this gas, it burns with a dull-red 
flame, and a thick cloud of smoke. The explanation is 
this : Chlorine has a strong affinity f ol* hydrogen, and 
but little for carbon. It therefore unites with the hy- 
drogen of the taper or candle, and the flame, heating 
the carbon that is with the hydrogen in the taper, sends 
it upward in a dense smoke. 
So, also, if a slip of paper, moistened with oil of turpentine, 
be introduced into a bottle of chlorine (Fig. 37), the hy- 
drogen of the turpentine will burn, while its carbon will 
pass ofiE unburned in smoke. 

We have just mentioned that hydrogen combines with 
chlorine, but we have not told you what substance is 
formed by their union. It is the "hydrochloric acid" 
which we have several times mentioned. You see the 
first part of the name comes from hydrogen^ and the last 
from chlorine^ its name thus indicating its composition. Hy- 
drogen gas, you know, is the lightest known substance, and 
burns with a very hot flame; chlorine you have just learned 
about. Kow, there is one thing very curious about these two 
gases when they are mixed together. If they be mixed in the 
dark, and be kept there, they have no disposition to unite ; but 
bring the mixture into the light, and the union takes place, form- 




CIILOEINE AND COMMON SALT. 



123 



Preparation of a solution of hydrochloric acid gas. 



ing the acid. If a beam of sunlight be thrown by reflection 
from a looking-glass npon the glass jar containing the mixture, 
the union is so rapid as to cause a violent explosion. This is a 
dangerous experiment, and we advise you not to try it. A sim- 
ple and safe way of making hydrochloric acid is to heat common 



Fig. 38. 



salt with sulphuric 
acid in a flask : the 
gas rises, and may 
be collected in 
bottles, or caught 
in water, in which 
it is very soluble. 
Fig. 38 represents 
an apparatus for 
obtaining a quan- 
tity of the gas dis- 
solved in water. 
The materials are 
placed in the flask at the left hand, and heated over the small 
furnace ; the gas passes out through the small tube into the first 
three-necked bottle which contains some water. When the water 
in this bottle will absorb no more, the gas passes over into the 
second bottle, and so on. The gas has a suffocating odor, but 
not so strong as chlorine, nor so disagreeable in its effects. 

What we commonly call hydrochloric acid is this solution of 
the gas. A mixture of this acid with nitric acid is called aqua 
regia^ that is, royal water, because it is the only liquid that will 
dissolve gold, the king of metals. It is very curious that neither 




124: CHLOEmE AND COMMON SALT. 

Occurrence of salt. Salt lakes and springs. 

of these strong acids alone can affect the gold ; but let them make 
the attack together, and this king submits at once. The gold, 
in dissolving, is changed into a chloride of gold. 

See how very widely both of the ingredients of common salt 
differ from the compound which they make. Chlorine is a 
gas of most powerful odor, very suffocating, so that to breathe 
it undiluted is to die. Sodium is a metal which, if put on your 
tongue, would take fire, and act as a caustic. Yet this gas and 
metal together form a very mild, pleasant salt, which is a part 
of the food of man and beast everywhere. 

Salt is a very abundant article in all parts of the world. There 
are large quantities of it dissolved in sea-water. In some parts 
of the world there are vast deposits of solid salt. The most fa- 
mous are those of Poland and Hungary. In the salt-mines of 
Cracow, though salt has been taken from them for over six hun- 
dred years, it is supposed that there is still enough to supply the 
whole world for centuries to come. Some parts of these mines 
have been shaped into beautiful forms of various kinds as the 
salt has been taken out. Chapels, halls, etc., have been made, 
the roof being supported by huge pillars of salt. When lighted 
up by lamps and torches the appearance is very beautiful. 

Large lakes of very salt water exist in many parts of the 
earth. There is a remarkable one in this country called Great 
Salt Lake. 

In this country most of our salt is obtained from salt-springs. 
The most noted are those of Salina and Syracuse. In the best 
of the springs there is a bushel of salt in every forty gallons of 
the brine. This is between eight and nine times as much as 



CHLORINE AND COMMON SALT. 125 

Mauufacture of salt. Calomel and corrosive sublimate. 

there usually is in sea- water. To get the brine from the springs 
wells are dug, and the brine is pumped up by machinery, and 
conducted by troughs to boilers. Here the water is driven ofi 
by heat. 

Sometimes the salt is obtained from the brine by a slower 
process. The brine is exposed to the sun in extensive shallow 
vats, and the water gradually passes off into the air, leaving the 
salt behind. Salt is often obtained in this way, in hot climates, 
from sea-water. 

There are a great many chlorides besides the chloride of so- 
dium, for chlorine unites with many of the metals. With some 
it unites with such eagerness that they burn together. Thus, if 
you sprinkle a fine powder of the metal antimony into a jar of 
chlorine gas, each particle will take fire. You will therefore 
have a shower of fire in the jar, and there will be a white smoke. 
This smoke is composed of very small particles of chloride of 
antimony, for in the burning the chlorine and antimony unite. 

There are two chlorides of mercury, which are very different 
from each other. One is calomel, and the other is corrosive sub- 
limate. The difference in their composition is that the corrosive 
sublimate has exactly twice as much chlorine in it as the calo- 
mel. The calomel is called, therefore, the chloride of mercury, 
while the corrosive sublimate is the bichloride. This difference 
in the proportion of chlorine makes a vast difference in tlie 
qualities of the two substances. The corrosive sublimate is very 
soluble in water, but the calomel will not dissolve at all. The 
corrosive sublimate is a violent eating or corrosive poison, as its 
name indicates. Sometimes, from carelessness, this poison has 



126 CHLOEmE AND COMMON SALT. 

Antidote to poisoning by corrosive sublimate. 

been drunk, and many deaths have been caused in this way. 
Now, every body ought to know exactly what to do when this 
accident happens, for what is to be done must be done quickly. 
The person must be made to swallow very freely of the whites 
of eggs. This is the best thing ; but, if eggs are not at hand, 
milk, or flour stirred up in water, can be used. 

Questions. — What are the chemical name and composition of common salt ? What 
are the properties of chlorine ? What is said of its purifying power ? What of its 
odor ? What of its bleaching power ? TeU about the solution of it. What is the 
use of chlorine in paper-making ? State the difference between grass-bleaching and 
the bleaching with chlorine. Describe some methods of obtaining chlorine gas. 
From what does the chlorine come in the second method ? Will substances burn in 
chlorine gas ? Of what is hydrochloric acid made ? Describe a safe way of obtain- 
ing it. What is aqua regia, and why so named ? What is said of the difference be- 
tween common salt and each of its ingredients ? What is said of the abundance of 
salt ? What of the salt-mines of Cracow ? What of salt-lakes ? What of the salt 
obtained in this country ? How is the salt obtained from the water containing it ? 
What slower process is sometimes employed ? What is said of antimony burning in 
chlorine ? What of the two chlorides of mercury ? What are their common names, 
and what their chemical names ? What should be done in case of poisoning by cor- 
rosive sublimate ? 



IODINE AND SEA-WATER. 127 

Occurrence and properties of iodine. Experiment. 



CHAPTEE XXIL 

IODINE AND SEA-WATER. 

There is another substance, similar to chlorine in many re- 
spects, in sea-water and in sea-plants. It is called iodine. It ex- 
ists in sea-water combined with the metals sodium and potassi- 
um, as chlorine is combined with sodium. In some sea-plants 
there is considerable of it, and it is from a lye made with the 
ashes of such plants that it is obtained. 

Iodine is a solid substance, looking something like graphite 
but darker in color. If heated, it turns into a splen- Fig. 39. 
did purple vapor or gas, which is one of the heaviest 
of the gases. If you put a few grains of it in a jar, a^ 
Fig. 39, and place the jar in a sand-bath,"^ &, warmed 
by a spirit-lamp, c^ the jar will be filled with the beau- 
tiful violet vapor. The air in the jar, being very 
much lighter than the iodine vapor, is pushed up by 
it out of the jar. When the jar is full of the vapor, place a 
piece of glass over it, and take it out of the bath. 

A taper will burn in this vapor, but not so brightly as in the 
air; but a piece of phosphorus will take fire of itself in it, so 
eager are the iodine and phosphorus to unite. If some iodine 

* A sand-bath is simply fine sand in a dish. The object is to apply the heat grad- 
ually. This can be done, however, with a spirit-lamp alone, by keeping it at a little 
distance from the glass jar. 




128 



IODINE a:n"d sea-water. 



Compounds of iodine. 



Bromine. 




be placed in a jar upon a little stand, with a bit of dry plios- 
Fig. 40. pborus upon it, as represented in Fig. 40, so much, 
heat results from their union that they take fire, 
and a smoke arises. This smoke is partly the vio- 
let vapor of the iodine and partly the white fumes 
formed by the phosphorus. 

As chlorine forms chlorides with many of the 
metals, so iodine forms iodides with them. The 
iodide of potassium is a very valuable medicine. Iodine forms 
two iodides with mercury, one of which is of a brilliant scarlet 
color. The iodide of silver is made use of in photography. 

There is another very singular substance in sea-water called 
hromine. This is a very heavy, reddish-brown liquid, giving out 
deep orange-colored fumes. The quantity of bromine in sea- 
water is very small. It seems to be quite essential, however, for 
it is always present. It is also in most salt springs. Wherever 
there is chlorine, bromine is found with it. It must be of some 
use in the sea-water, but what we know not. It never exists in 
the sea- water as bromine, but is always in combination with such 
metals as sodium and magnesium, making bromides. The chem- 
ist can separate it from these. 

This very singular substance is a terrible poison. A single 
drop on the skin eats into it and makes a painful sore. Bromide 
of sodium is used in photography and in medicine. 

The three substances of which we have spoken in this and the 
previous chapter (chlorine, iodine, and bromine) are the peculiar 
substances of sea-water. They are always united, however, with 
other substances, making compounds, chlorides, iodides, and bro- 



IODINE AND SEA-WATER. 129 

The substances which are in sea-water. 

mides. The reason that the water of the sea has so much of 
these and various other mineral substances in it is, that in the 
sea are collected the washings from all kinds of rocks and sand 
and earth. The different salts thus collected and dissolved in 
the sea are these : chloride of sodium, or common salt ; chloride 
of potassium ; chloride of calcium ; chloride of magnesium ; sul- 
phate of lime, or gypsum ; sulphate of magnesia, or Epsom salts ; 
carbonate of lime, or chalk ; carbonate of magnesia. These are 
always present in sea-water, besides various other substances. 

We can learn of what use some of these substances are in 
the sea. For example, we can see of what use carbonate of lime 
is. All those animals that live in shell houses, as you learned 
in Chapter XYIII., need carbonate of lime in the water they 
drink, so that it may get into their body, and be used in mak- 
ing their shells. 

Most of the solid matter dissolved in sea-water is common salt. 
Next to this in quantity are the compounds of magnesium — the 
chloride of magnesium, and the sulphate and carbonate of mag- 
nesia. It is these that give the bitter taste, especially the sul- 
phate of magnesia, or Epsom salts. If you ever take any of this 
as a medicine, you will recognize the resemblance between its 
taste and the bitter taste of sea-water. 

There is a comparatively small amount of these saline matters 
in rivers, because the water in them is always moving on to empty 
into lakes and seas. There is usually but little in lakes, because 
the water is running out of them as constantly as it runs in. Thus 
the water that runs into our great chain of lakes in the north runs 
out through the Eiver St. Lawrence into the Atlantic Ocean. 



130 



IODINE AND SEA-WATER. 



Water of the Dead Sea very heavy. 



Some inland seas and lakes contain more saline matters than 
the ocean itself. This is partly because they have no outlet, 
and partly because there is much salt in the neighborhood. 
The Caspian Sea, the Dead Sea, and the Great Salt Lake of 
Utah are of this kind. 

All the saline matter in the water of rivers, and lakes, and 
seas was once in the rocks of the earth, and was carried off 
by the water, which is everywhere so bnsy. But, for the most 
part, before this was done, such matter was in various ways 
broken off from the rocks, and ground up, so as to make a part 
of the earth under our feet. Here the water found it, and car- 
ried it off into the brooks and rivers and seas. 

But much of all this is returned, in various ways, from the 
water to the earth again. We will give but one example of 



Fig. 41. 




this. The coral animals, about which you 
learned in Chapter XVIII., taking the car- 
bonate of lime which the earth has sup- 
plied to the water, give it back to the 
earth in reefs and islands. 

The more salt there is in water, the 
heavier it is, and the more easily will it 
bear up solid substances. Thus, a man 
floating in common water has only a part 
of his head above the surface ; but in the 
water of the Dead Sea it costs him no ef- 
fort to keep breast-high in it. A ship 
there would easily carry a load which 
would sink it almost anywhere else. 



IODINE AND SEA-WATEB. 



131 



Experiments. 



The egg will remain at 



Fig. 42. 



There are some pretty experiments which show the difference 
between salt and fresh water in regard to floating substances. 
Suppose that you have an egg in a jar half full of water. The 
egg will be at the bottom of the jar, for it is heavier than water. 
Pour now some strong brine into the bottom of the jar through 
a long tube, as represented in Fig. 41. The brine will force up 
the lighter water, and with it the egg. 
the middle part of the jar, at the 
bottom of the fresh water, floating 
on the brine, just as a piece of 
wood would float on the surface 
of water in the jar, at the bottom 
of the air, if the jar were half full 
of water. 

A very pretty experiment is 
represented in Fig. 42. The jar 
A is filled with brine. A little 
toy ship, so loaded that it will just 
float upon the brine, is placed upon it. 





If now you place the 
ship in the jar of fresh water, B, it will sink. 

Questions. — Where is iodine found ? Describe this substance. What are iodides, 
and what is said of some of them ? Describe bromine. What is said of the quantity 
of it in sea- water ? With what is it united ? What is said of its poisonous charac- 
ter ? To what use has it been appUed ? What is said of the three substances pecul- 
iar to sea-water ? What are the solid substances contained in sea-water ? Of what 
use is the carbonate of lime in sea-water ? What is said of common salt ? What is 
the cause of the bitter taste of sea-water ? What is said of solid matter in the water 
of rivers and lakes ? Mention some inland lakes and seas that are salt. Why are 
they so ? Describe the experiment with the egg. With the toy ship. 



132 SOLUTION AND CRYSTALLIZATION. 

Solubility of salts. Advantage of different degrees of solubility. 



CHAPTEE XXIII. 

SOLUTION AND CRYSTALLIZATION. 

The different substances of which we have been wTiting vary 
greatly as to their solubility in water : some of them will not 
dissolve at all, some sparingly, and water will absorb large quan- 
tities of some others. Calomel, for example, which is a chloride 
of mercury, is perfectly insoluble ; that is, not a particle of it 
can be dissolved in water. But corrosive sublimate, the bichlo- 
ride of mercury, is very soluble. Magnesia is insoluble, but 
potash is exceedingly soluble. The latter is very eager for wa- 
ter, and if exposed will become dissolved in the water which it 
gathers from the air. It can be dissolved in half its weight of 
water ; that is, a pound of water will dissolve two pounds of 
potash. Now, lime absorbs water, but it takes seven hundred 
pounds of water to dissolve one pound of lime. 

The Creator has made this great difference between potash and 
lime, in regard to solubility, because the difference is needed. For 
example, we want to use lime in plastering walls ; but it would 
not answer for this if it would, like potash, gather water from 
the air and dissolve in it. It would be very inconvenient to have 
the plastering in our houses dissolve and run down whenever it 
chanced to get wet. But for the uses for which man needs pot- 
ash it is well to have it dissolve easily. For instance, it is used 
in making soap, and needs to be soluble for this purpose. 



SOLUTION AND CRYSTALLIZATION. 133 

Solubility of salt. Carbonate of lime and of soda contrasted. 

Salt dissolves easily, but not so easily as potash. It would be 
inconvenient to have it do so. We want to keep salt dry for 
use, and this we could not do if it absorbed water as eagerly as 
potash. The Creator has made it soluble to just the right de- 
gree to suit the uses for which he designed it. It sometimes 
troubles us by gathering moisture from the air, but this is only 
when the weather is damp ; that is, when the air has much wa- 
ter in it. 

Let us compare two carbonates in regard to solubility, the 
carbonate of soda and the carbonate of lime. The carbonate of 
soda is very soluble. This is convenient for the uses to w^hich 
man puts this salt. But the carbonate of lime, w^hich appears 
in the forms of chalk, limestone, marble, etc., is very slightly 
soluble. It would be bad to have it dissolve readily in water. 
This salt, you know, makes the shells of oysters and other shell- 
fish. It would not be well to have their shell houses made of a 
material that the water could dissolve easily. And yet, if car- 
bonate of lime were not somewhat soluble, how could it get into 
the blood of these animals so that it can be made into shell? 
You see, then, that the Creator has made this all just right. 

But, besides this, it would be very injurious to have so much 
carbonate of lime in the water as there would be if it were very 
soluble. The rain that comes down upon chalk and limestone, 
which here and there form rocks and hills, and even mountains, 
always washes down a little, and carries it among the particles 
of the earth, and down streams into the ocean. That little is 
enough for building the houses of shell-fish and for other pur- 
poses. If the carbonate of lime were more soluble, there would 



134: SOLUTION AND CEYSTALLIZATION. 

Silica. Saturation. What it is to dissolve a substance. 

be more than enough, and it would give us a great deal of 
trouble. When well-water is hard^ it is generally because there 
happens to be considerable carbonate of lime in it. 

Silica is, like carbonate of lime, but slightly soluble. Suppose 
that it were not soluble at all ; all our grass and grain would lie 
flat along the ground, for it is the silica in them that gives them 
the firmness by which they stand up. 

Commonly, when a substance is soluble, more will dissolve in 
hot than in cold water, but this is not so with common salt. 

"When we have made water dissolve just as much of a sub- 
stance as it can, we call it a saturated solution. This word 
comes from a Latin word which signifies to satisfy, or feed to 
the full. Water is more easily satisfied or saturated with some 
substances than with others. Potash and lime are in strong con- 
trast in this respect : half of a pound of water will not be sat- 
isfied till it has dissolved a pound of potash, while seven hun- 
dred pounds of water wdll be satisfied or saturated with a pound 
of lime ; that is, it takes fourteen hundred times as much pot- 
ash as lime to saturate water. 

Observe what it is to have a solid substance dissolved in wa- 
ter. Some solid substances you can mix up very thoroughly 
with water by powdering them well, and yet they do not dis- 
solve. Calcined magnesia is readily mixed with water, but it is 
not dissolved, and it settles after the water has stood for a little 
while. But a substance that dissolves disappears. If it have 
color, you see that in the water, but not the little grains or par- 
ticles, as you do in the magnesia and water. A perfect solution 
is generally clear and transparent. The substance dissolved is 



SOLUTION AND CEYSTALLIZATION. 135 

Water dissolved in air. Crystallization of alum. 

much more finely divided up than when it is merely mixed in 
the water ; and if the solution be left to stand, the solid sub- 
stance remains, as we may say, hidden among the particles of 
the water. 

Somewhat in the same way that water dissolves solids, air dis- 
solves water. In the clearest day, when the air appears to us to 
be dry, there is a great deal of water in the air ; you do not see 
it for the same reason that you do not see a solid substance 
when it is dissolved in water. The water is dissolved in the air ; 
and hot air will dissolve more water than cold, just as hot water 
will dissolve more alum than cold water. "When water gathers 
on our cool tumblers in hot weather, it is because the hot air all 
around the tumblers has so much water dissolved in it. 

As crystals are often formed from solutions, it is proper to 
speak here of crystallization. 

Hot water will dissolve twice as much alum as cold water. If 
you dissolve, then, as much as you can of alum in hot water, 
that is, make a saturated solution, when the water becomes cold 
half of the alum will become solid again ; and in doing so it will 
gather in crystals upon the bottom and sides of the vessel. If 
you suspend a wire in the vessel of dissolved alum, as it cools 
the crystals will collect upon this wire. You have, perhaps, 
seen baskets made of alum or other crystals. They were made 
in this way : the basket, made of bonnet- wire, was suspended in 
a hot solution of alum, and the crystals formed upon all parts of 
the wire. 

When the substance used dissolves as freely in cold as in hot 
water, as is the case with common salt, crystallization is pro- 



136 SOLUTION AND CRTSTALLIZATION. 

Wonders of crystallization seen in ice and snow. 

duced only by evaporation. As tlie water goes off into the air, 
the crystals form. 

How beautiful and curious a process crystallization is ! In 
what exact order are the particles arranged to make such very 
smooth surfaces and such straight edges ! They are particles, 
remember, that are so small that we can not see them even with 
a powerful microscope ; and yet, in forming a crystal, each one 
is made by the Creator to take its right place. Sometimes the 
particles arrange themselves very quickly. The most familiar 
example we have of this is in water. Sometimes, on taking up 
a pitcher of water on a cold morning, a great part of the water 
turns all at once into crystals, which shoot across in the pitcher 
in every direction. If you pour out what water remains fluid, 
you can see the crystals. The explanation of this is easy. The 
water in the pitcher during the night became freezing cold, but 
it was perfectly still, and so the particles of the water remained 
motionless; but the shaking given to them by taking up the 
pitcher made them arrange themselves in the solid crystalKne 
form. 

We have the same quick formation of crystals, on a large 
scale, in every snow - storm. The clouds are the reservoirs of 
water from which the snow is made, the water in them being 
in the form of fog ; and the particles of this fog are in a snow- 
storm continually arranging themselves in crystals, and so fall to 
the earth. 

There are great varieties in crystalline arrangement. We will 
point out some of them. Mica, a mineral used for windows in 
stove doors, is arranged in leaves which you can peel off exceed- 



SOLUTION AND CRYSTALLIZATION. 



137 



Crystals of mica, salt, Iceland spar, gypsum, and water. 





Fig. 43. 






^\ 






^ 




ingly thin. The sheets of mica, or isinglass, as it is commonly 
called, used for this purpose are really made up of very many 
of these thin leaves. In Fig. 43 ^j^ ^g^ ^.^ ^ 

you see the shapes of the crys- 
tals of common salt. They are 
cubical blocks. And in Fig. 
44 you see the forms of the 
crystals of a very beautiful min- 
eral called calc spar, or some- 
times Iceland spar, because it was first brought from Iceland. 
It is composed of the same things as common chalk. You see 
that the crystals are not cubical, like those of salt, but they are 
sloping. These are but two of the very many varieties that oc- 
cur in the shapes of crystals. Sometimes the same substance ap- 
pears in many different forms. This is the case with gypsum, 
as noticed on page 102. 

In the crystals of some salts there is water locked up and con 
cealed, but in some there is none. In carbonate of lime there is 
no water, but only carbonic acid and hme. In crystallized car- 
bonate of soda, on the other hand, thera is more of water than 
there is of carbonic acid and soda together. In 100 pounds of 
this salt there are 63 pounds of water. Yet the crystals are dry ; 
for the water is a part of the solid substance, locked up with the 
carbonic acid and the soda. You can get this salt without any 
water in it by heating it ; but the first thing it does on applying 
the heat is to melt in its own water. As you continue the heat 
you drive off this water into the air, and the powder of the salt 
is left behind. It is no longer crystalline ; for it can not be so 



138 SOLUTION AKD CEYSTALLIZATION. 

Water of crystallization. Gunpowder. Deliquescing and efflorescing. 

without its supply of water, or its water of crystallization. By 
this term we mean the amount of water which is contained by 
any substance w^hen in a crystalline form. This varies in dif- 
ferent substances. Some require no water, some a little, and 
some a great deal. 

Nitrate of potash, or saltpetre, has no water in it. If it had, 
it might not answer so well for making gunpowder. Nitrate of 
soda has no water in it, and it would do for making gunpowder 
as well as the nitrate of potash, were it not for one thing : it 
gathers moisture from the air. This would not answer for pow- 
der, for powder must be kept dry. A salt which thus gathers 
moisture from the air is said to deliquesce — a word which comes 
from a Latin word meaning " to melt.'' A salt, on the other 
hand, which, on exposure, loses its water of crystallization, and 
changes from a crystal into a powder, is said to effloresce. 
Crystals that do this have a mealy powder gradually form on 
their surface. The word " effloresce " comes from a Latin word 
meaning " to flower." It is as if the mineral flowered out. 

Many of the metals exist in crystals. "We shall describe a beau- 
tiful experiment by which you can easily obtain lead in crystals. 

There is a substance made of acetic acid (the acid of vinegar) 
and lead, commonly called sugar of lead, because it has a sweet 
taste. You must not taste it, however, because it is poisonous. 

Dissolve half an ounce of sugar of lead in six ounces (twelve 
table-spoonfuls) of water, in a bottle. Fasten to the cork a rod 
or stick of zinc, and hang it in the solution, as shown in Fig. 45, 
on the following page. Tou will soon see a change taking 
place. The zinc will begin to have little spangles upon it, and 



SOLUTION AND CRYSTALLIZATION. 



139 



The lead tree. 




these will gradually brancli ont in all directions, forming 
of tree. This tree is made of the metal lead, and 
is called the lead tree. The explanation is this : 
the acetic acid leaves the lead and unites with the 
zinc to form acetate of zinc. The lead, which is 
separated from the acid, forms the tree, while the 
acetate of zinc dissolves in the water, taking the 
place there of the acetate of lead. It takes a day 
or two for the tree to be completed. If, on making 
the solution in the bottle it is not perfectly clear, 
you can make it so by adding a little good vinegar. 

Questions. — Give some illustrations showing the variety as to solubility of sub- 
stances. Show the necessity for the difference in regard to lime and potash. What 
is said of the solubility of common salt ? What of the solubility of carbonate of soda 
and carbonate of lime ? What would be the difficulty with shell-fish if carbonate of 
lime were very soluble ? Why is it necessary for them that it should be a little sol- 
uble ? How does carbonate of hme get into the sea ? What is one of the causes of 
the hardness of well-water ? What is said of silica ? What is said of hot and cold 
water in dissolving substances ? What is a saturated solution ? State the difference 
between potash and lime in saturating water. Explain what solution really is. What 
is said of the solution of water in air ? What of making crystals of alum ? What is 
said of the process of crystalhzation ? State the example given of sudden crystalliza- 
tion. What is said of crystallization in a snow-storm ? Describe the three varieties 
of crystalline forms that are given. What is said of the same substance appearing 
in various forms ? Give in full what is said of the water of crystallization. What is 
deliquescence ? What is efflorescence ? Describe the method of obtaining lead in 
crystals. Explain the chemistry of the operation. 



140 WOOD. PETEOLEUM. 



Inorganic aud organic chemistry. Organized bodies. 



CHAPTEE XXIV. 

WOOD. PETEOLEUM. 

So far, yoTi have been learning chiefly about the chemistry of 
onineral substances, but we will now tell you something about 
the chemistry of vegetable and animal substances. Mineral 
chemistry is sometimes called Inorganic chemistry, and the 
branch of chemistry explained in the remaining chapters is 
called Organic chemistry. Most people, when the term mineral 
substances is used, think that solid substances only are meant ; 
but air and water are as truly mineral substances as the crystals 
on the shelves of a cabinet, or the stones and rocks around you. 
Organic chemistry teaches about wood, sugar, alcohol, starch, 
gum, the substances in the flesh and other parts of animals ; and 
since these all contain carbon^ about which you learned in Chap- 
ter Y., organic chemistry is often called the chemistry of car- 
bon. It was formerly thought that such substances as alcohol, 
acetic acid, indigo, and the like, could be produced only through 
the agency of a living force ; but we now know that these very 
substances can be made artificially in the laboratory. 

You must not think that all organic substances can be rdade 
by the chemist. Certain substances having a peculiar structure, 
easily recognized by a microscope, can not be made in the lab- 
oratory. Starch is one of these, cotton is another. These are 
called organized bodies, because they have an organized structure. 



WOOD. PETROLEUM. 141 



Man can not make wood. A contrast. 

We have told you already something about the chemistry of 
vegetables in speaking of carbon as entering into the leaves and 
making a part of the wood of trees. Now, wood is composed of 
three things : carbon, oxygen, and hydrogen. Yon see that it is 
composed of a sohd united with two gases. When we make 
charcoal out of wood, as described to you on page 31, we decom- 
pose the wood. We send off its oxygen and hydrogen into the 
air by the heat of the burning, and most of the carbon is left 
behind. We say most of it, but not all, for some of the car- 
bon unites with the oxygen in the combustion, and flies off as 
carbonic acid gas. 

Though you can thus decompose wood, you can not take the 
ingredients and unite them so as to make wood of them. If 
you mix up powdered charcoal with water, you have all of the 
ingredients of wood together ; but you can not in any way make 
them combine to form wood. So you have the ingredients of 
wood if you put charcoal into a jar filled with oxygen and hy- 
drogen gases, but they will not turn into wood ; they will re- 
main unchanged. If you light up the charcoal before you put 
it into the jar, an effect will be produced, but no wood will be 
made ; an explosion will take place, the oxygen and hydrogen 
uniting with great violence, forming water, and some of the oxy- 
gen uniting with the charcoal to form carbonic acid gas. 

See how different this is from what we can do with some of 
the minerals that we have told you about. For example, take 
sulphate of copper or blue vitriol. This is composed of three 
things : sulphur, oxygen, and copper. Now, we can make the 
sulphur and oxygen unite to form, in the presence of water, sul- 



142 WOOD- PETROLEUM. 



How wood is made. Varieties of wood. 

phuric acid, and then this acid will unite with the copper, form- 
ing the sulphate of copper. 

But although we can not in any way make the ingredients of 
w^ood unite to form wood, it is done in the tree. Let us see 
how. Much of the carbon is furnished from the air, being taken 
in by the leaves from the air, as you learned in Chapter VII. 
Then the water that comes up in the sap from the roots fur- 
nishes the oxygen and hydrogen ; for water, you know, is com- 
posed of these two gases. We may say, then, that the tree 
makes its own wood out of charcoal and water. 

"Wood in every tree is composed of the same things — carbon, 
oxygen, and hydrogen — although the trees are so different ; and 
there is more difference in the ways in which wood is put to- 
gether in different trees than you would suppose from looking 
at the outside, or from seeing the wood itseK with the naked 
eye. The microscope shows astonishing differences. In order 
to see these, exceedingly thin shavings, of various kinds of wood, 
are cut with a very sharp instrument across the grain of the 
wood. On examining these with the microscope, they are so 
much magnified that we can see just how each kind of wood is 
put together. In some, as the pine, there is a very open net- 
work, with here and there large round openings, while in other 
more solid woods the spaces are much smaller. These spaces 
have very great variety of arrangement in different kinds of 
wood, and in some the arrangement is exceedingly beautiful. 

But there is stiU more variety in wood than we have yet told 
you about. There are a great many other things which are re- 
ally wood besides those which people commonly call by this 



WOOD. PETEOLEUM. 143 



Bark, leaves, flowers, stalks, etc., are different forms of wood. 

name. Tlie bark of trees is wood, only in a different form from 
tlie wood which it covers, very much as chalk or the common 
limestone differs from marble. Hold a leaf up so that the light 
can shine through it. All that delicate frame-work that you see 
is a wooden frame-work. More than this, the skin of the leaf 
and all its substance are wood. The whole leaf is wood except 
the sap that is in it, and that which gives it its beautiful color ; 
and what we have said of leaves is true also of flowers. The 
most delicate flower that you can find is made of wood ; very, 
very fine and delicate is such wood, and yet it is wood. Every 
stalk of grain and blade of grass is made up chiefly of wood. 
Cotton or linen fibre is woody fibre. 

All paper is wood. It is made, when it is fine, as writing-pa- 
per, of cotton and linen rags, and these are wood. If you tear 
a piece of letter-paper, and look at the torn edge through a mag- 
nifying - glass or a microscope, you will see very plainly the 
woody fibres pointing out in all directions from the edge. In 
paper these fibres are not regularly arranged as in the cotton 
after it is gathered, but they are mingled together in all sorts of 
ways, lying across each other in confusion. 

All the frame-work, as we may call it, of fruits is wood. All 
the partitions in fruits are wooden partitions — as, for example, 
in the orange. 

The coverings of all seeds are wood. In some of the nuts 
the woody substance forming their covering is very dense and 
hard, as in the cocoa-nut, the walnut, etc. The substance called 
vegetable ivory is wood very closely put together. 

We put woody fibre to a great variety of uses. We build 



144 WOOD. PETEOLEUM. 



Origin of coal. Varieties of coal. 

houses with, it, and fill them with wooden furniture. We make 
ships, carriages, bridges, of wood, and in some countries even 
shoes are made of it. Out of woody fibre we make thread, 
twine, cordage, and fabrics of every variety. We clothe our- 
selves with it ; we write and print upon it ; we even eat it as 
part of our food ; we burn it to keep ourselves warm, and to do 
our cooking. "We spread it out in huge sheets to the wind in 
our boats and ships. 

All the coal in the earth was once wood. Immense forests 
covered the earth, which, in the course of time, became buried 
in the earth, and were converted into coal by the action of heat 
under pressure. The decomposition of the wood went on very 
slowly, the hydrogen and the oxygen passing off for the most 
part, and the carbon remaining. 

The change is something like that which wood undergoes 
when heated strongly in a close vessel, as ex]3lained in the ex- 
periment illustrated by Fig. 9, on page 32. 

Some kinds of coal are much more wood-like than others. A 
brown kind, which retains partly its woody structure, is called 
lignite; then we have bituminous coal^ which burns with a 
smoky flame ; and, finally, hard coal, or anthracite^ which is the 
coal commonly burned in our furnaces and grates. 

Coal is not pure carbon ; if it were, we could not make any il- 
luminating gas from it, for this gas contains hydrogen combined 
with carbon. When coal is heated in large iron retorts in the 
gas-houses, besides the gas, a substance called coal-tar is ob- 
tained, a black, sticky material of disagreeable odor, and which 
you would not care to have any thing to do with. Yet from 



WOOD. PETROLEUM. 145 



Origin of petroleum. Kerosene. 

this once valueless substance many of our most beautiful dye- 
stuffs have been manufactured, especially certain shades of vio- 
let and red, known under the name of aniline colors. 

Coal buried in the earth has been heated by natural fires, in 
a somewhat similar manner, and this has furnished us that valu- 
able material, petroleum. Petroleum, obtained by pumping out 
wells bored in the oil regions, is a mixture of many liquid and 
sohd bodies composed of hydrogen and carbon. When it issues 
from the earth, it is dark-colored and ill-smelling, and must be 
refined by a peculiar process. This separates the petroleum into 
several liquids, of which the most useful are : gasolene, naphtha, 
benzine, kerosene, lubricating oil, and a solid body called par- 
aifin. Gasolene is used in making " air-gas ;" naphtha, for paints 
and varnishes, and for cleansing greasy articles; kerosene, for 
burning in lamps ; and paraffin, in making candles. 

Naphtha and benzine are very light liquids, and readily rise in 
vapors, which, mixed with air, make very explosive gases. When 
kerosene contains these substances, especially benzine, it is very 
dangerous. Hefined kerosene is safe to burn in lamps ; but in 
order to sell it cheap, manufacturers sometimes mix benzine with 
it, and this gives rise to many sad and terrible accidents. 

Questions. — ^What does organic chemistry teach ? Can organic substances be made 
by the chemist ? Name some substances having an organized structure. What is said 
about the composition of wood ? What is done to wood in making charcoal ? What 
is said about making wood ? How is wood formed in the tree ? What is said of the 
different varieties of wood ? What of its uses ? What is the origin of coal ? Name 
the three kinds of coal. What is coal-tar ? What is manufactured from it ? What 
is the origin of petroleum ? What is said of it ? What are the useful materials 
obtained by refining it ? What is said of kerosene ? 

K 



146 



STARCH AND SUGAR. 



Starch in the vegetables that we eat. 



Arrowroot. 



CHAPTEE XXV. 



STARCH AND SUaAR. 



Fig. 46. 



Starch is a very common substance in vegetables. It is not 
so common as wood, for that, as you have learned, is in every 
part of all vegetables, from the largest trees to the smallest plants. 

There is more or less 
starch in all the vegeta- 
ble substances we eat. 
Four -fifths of the flour 
of which our bread is 
made is starch. Most 
of the potato is starch. 
There is much of it in 
chestnuts, and even in 
horse-chestnuts it consti- 
tutes one -eighth of the 
whole. Arrowroot is a 
starchy meal, prepared 
from some plants that 
grow in marshy grounds 
in warm climates. Sago 
is a starchy substance, 
prepared from the pith of various kinds of palm-trees. From 
all this you see that a large part of the food of man is starch. 




STAECH AND SUGAR. 



147 



IIow to obtain starch from flour. 



Composition of starch. 



Sources of sujrar. 



Fi^. 4T. 



You can very readily obtain starcli from wheat flour. Moist- 
en a handful of it with enough water to make a thin paste. Put 
this into a piece of thick linen cloth and knead it, adding water 
to the paste as long as the liquid which runs through the cloth 
appears milky. Let the liquid in the vessel stand for some time, 
and a white powder will settle at the bottom. This is wheat 
starch. What remains in the cloth we will tell you about in the 
next chapter. 

The starch forms grains, and each little grain, as seen by the 
microscope (Fig. 47), has a covering. Now, in boiling starch it 
swells up into a thick jelly. In 
this operation the coatings of 
the grains are broken, and the 
starch absorbs considerable wa- 
ter. This is the reason that rice, 
beans, barley, etc., swell so much 
when they are cooked. Chest- 
nuts swell when you boil them, 
from the same cause. 

You will be surprised to learn 
that starch, though so different 
from wood, is composed of the 
same elements — carbon, hydro- 
gen, and oxygen — and that, too, in the same proportions. It is 
deposited in those parts of the plant where it can be used for 
food, in the grains or seeds, and other fruits, as in the tubers 
of the potato-plant. 

Sugar is another substance found in many plants. All fruits 




148 STARCH AND SUGAR. 



How sugar is made iu plants. How sugar is obtained from the cane. 

that are sweet have sngar in them. Besides this, there are some 
plants which are designed by the Creator to make sugar for the 
use of man ; of these the most important are the sugar-cane, the 
sugar-maple, and the sugar-beet. In Germany and France, the 
sugar-beet is largely cultivated for the manufacture of sugar. 

Sugar, like starch and wood, is composed of carbon, oxygen, 
and hydrogen, but not in the same proportions. Although we 
can not make sugar by mixing these ingredients together, any 
more than we can wood or starch, yet this is done by the plants. 
Much of the carbon is taken from the air by the leaves, while 
the water comes up from the ground by the roots. The long, 
broad leaves, shaped much like corn-leaves, are spread out to the 
air to suck in, by their little and numberless mouths, the carbon 
from the air, so that there may be enough of this material for 
making the sugar. Now, as the carbon in the air comes in part 
from the breath of animals, it may be that some of the carbon 
in some of the sugar that you have eaten may have come from 
your lungs. If so, it flew a long way, on the wings of the wind, 
to the south, to get to the cane-leaf that drank it in. 

In obtaining sugar from the cane, the juice is first pressed out 
between heavy iron rollers. This juice is then cleared of most 
of its impurities, and is boiled down to such a degree that the 
sugar will crystallize as it cools. While this crystallization is 
going on, a sirup trickles from the sugar, and this is molasses. 
The sugar crystallizes in grains, forming the common brown sug-» 
ar. Further purification is required to make it into white sugar. 

There are different kinds of sugar. The two most important 
are grape-sugar and cane-sugar. Grape-sugar is that which is 



STAECH AND SUGAE. 149 



Difference between cane-sugar and grape-sugar. Sugar made from sawdust. 

found in grapes and in sweet fruits generally. Cane - sugar is 
that which is found in sugar-cane and other plants that are evi- 
dently designed by the Creator to manufacture sugar for our 
use. The cane-sugar has much greater sweetening power than 
grape-sugar, and therefore is more valuable. A single tea- 
spoonful of cane-sugar has as much sweetening power as two 
and a half tea-spoonfuls of grape-sugar. 

The difference in composition between these two kinds is that 
the grape-sugar has more of oxygen and hydrogen than the cane- 
sugar ; or, because oxygen and hydrogen are the two ingredients 
of water, some chemists say that grape-sugar has more water in 
it than the other. 

Though we can not take carbon and oxygen and hydrogen, 
and make them into wood, or starch, or sugar, we can make 
sugar out of either starch or wood. " What !" you will perhaps 
exclaim, " make sugar out of sawdust ?" Yes, exactly so. It can 
be done by heating with sulphuric acid diluted with water. The 
sawdust is first moistened with sulphuric acid, and left to stand 
for about twelve hours ; it becomes nearly dry, water is added 
and the mixture boiled ; the sugar is then formed. Being, how- 
ever, in the form of sirup, and mixed with the excess of sulphu- 
ric acid, the latter is first removed by means of chalk, and the 
remaining liquid is boiled down to get the sugar. This proc- 
ess will be explained in Hooker's Chemistry, Science for the 
School and Family, Part III. 

Sugar can be manufactured from rags as well as from wood ; 
for, as you have already learned, rags are nothing but wood in a 
certain form. 



150 STAKCH AND SUGAR. 



How plants convert sugar into wood. Maple-sugar. 

The process of converting starch into sngar is essentially the 
same. But what kind of sngar can thns be made out of such 
cheap materials as sawdust and rags? It is grape-sugar, and 
not the valuable cane-sugar. If we could manufacture cane- 
sugar in this way, we should not need to depend so entirely 
on the sugar-cane for our supply. 

We have told you that there is sugar in all sweet fruits ; but 
there is no sugar in them at first. They are either tasteless or 
acid, and become sweet as they ripen. Before they ripen there 
is starch in them, and this changes into sugar. 

Though we can make wood into sugar, we can not turn sugar 
into wood. This is done, however, by plants. Suppose we have 
a sugar -maple that has not been tapped by any one, what be- 
comes of all the sugar that is in it in the spring ? Does it stay 
there locked up for some one to get next spring ? If it does, 
what a quantity of sugar there will be for him, for he will have 
all that is made in two seasons ! But the sugar does not all stay 
there ; it circulates about in the tree, and helps to make leaves 
and bark and wood. But that sugar should be turned into wood 
is no more strange than that wood should turn into sugar ; and 
when we come to look into the whole matter, it is not so strange 
after all, for wood and sugar are composed of the same things 
— carbon, oxygen, and hydrogen. The proportions only need 
to be changed to convert the one into the other. 

We see the same change of sugar into wood in other vegeta- 
bles. Thus the sugar-beet and turnip are sweetest when gath- 
ered early. If allowed to remain growing too long, the sugar is 
changed into wood, and they become, therefore, tough and taste- 



STARCH a:nd sugar. 151 



How to make sugar-charcoal. 



less. So, also, if grass be left to grow too long, the starch and 
sugar in it turn to wood, and the hay is not so sweet and nutri- 
tious as it would have been if gathered earlier. 

We can make charcoal from sugar as well as from wood, since 
it is composed of the same elements. We can do it simply by 
heating the sugar; but a prettier way to do it is this : Put. a ta- 
ble-spoonful of strong sirup, made with loaf-sugar, into a tum- 
bler set in a large plate, and pour upon it a little good sulphuric 
acid. The acid sets free the charcoal, producing considerable 
heat. This makes a brisk bubbling-up, even over the sides of 
the tumbler. After the tumbler gets cool, pour the contents 
into the plate, and you have a specimen of sugar-charcoal. 

Questions. — What is said of the abundance of starch in plants ? Mention some of 
the vegetable substances in which it is found. What is arrowroot ? What is sago ? 
How can you obtain starch from wheaten flour ? What sort of a substance is starch ? 
What effect has boiling upon it ? What is said of the composition of starch ? 
Where in plants is it deposited ? What is said of sugar in vegetables ? What is 
the composition of sugar ? What is said about sugar in plants ? How is sugar ob- 
tained from sugar-cane ? What is molasses ? What are the two kinds of sugar, and 
how do they differ ? What is said of making sugar from wood ? From rags ? What 
of making sugar from starch ? What kind of sugar is made from these substances ? 
Why can not cane-sugar be made in this way ? What is said about sugar in fruits ? 
What about the change of sugar into wood in the sugar-maple ? In vegetables ? 
What is said of sugar-charcoal? 



152 GLUTEN AKD THE FOOD OF A>^IMALS. 

Nitrogen in all animal substances. Animals must have it in their food. 



CHAPTEE XXVI. 

GLUTEN AND THE FOOD OF ANIMALS. 

Tou see that vegetable substances are mostly made of carbon, 
oxygen, and hydrogen ; but animal substances, flesh, skin, hair, 
nerves, etc., are made of these same things, with another added, 
viz., nitrogen. It is this gas that makes the great distinction 
between animal and most vegetable substances. 

It is the nitrogen compounds in part that give the peculiar 
strong odor which we smell whenever any animal substance is 
burned. Wood, cotton, linen, etc., give out but httle smell when 
burned ; but let any woolen thing, or hair, or leather be burned, 
and the odor is disagreeable and strong : and it is very much 
the same in all these cases. 

As nearly all substances which are peculiar to animals have 
nitrogen in them, there must, of course, be some nitrogen in 
their food, for without this they would droop and die. It is the 
food that makes the blood, and the blood, as you learned in the 
Second Part of the Child's Book of Nature, is the building and 
repairing material of the body. Tou can see, then, that if no 
nitrogen be furnished to the blood, one of the four great mate- 
rials for building and repairing will soon be spent. The body 
wiU, therefore, in a little time, show this great want, and get 
out of repair ; and, if it remain long in this condition, it will 
die. To repair the body without nitrogen would be very much 



GLUTEN AKD THE FOOD OF ANIMALS. 153 

How animals get their nitrogen. Gluten. What it does to bread. 

like repairing a brick-wall without brick, filling up breaches in 
it with mortar alone. 

Now, you can readily see where some animals get that part of 
their building and repairing material which we call nitrogen. 
Lions, tigers, dogs, cats, etc., eat animal food, and there is nitro- 
gen always in that. But how is it with horses, cows, sheep, etc. ? 
"Where do they get their nitrogen? They eat no animal food, 
and the vegetable substances that we have told you about — 
wood, starch, and sugar — contain no nitrogen. There is a plenty 
of nitrogen all around them in the air, and they breathe it con- 
tinually into their lungs ; but not a particle of this gas gets into 
the blood. 

How, then, do the vegetable-eating animals get their nitrogen? 
We will tell you. You remember that, in describing the meth- 
od of obtaining starch from wheat flour, we said there was a 
substance left in the linen cloth ; this substance we call gluten — 
a very glutinous, or sticky, substance. This portion of the flour 
contains nitrogen. While the starchy part is composed of car- 
bon, oxygen, and hydrogen, the gluten is. composed of these and 
nitrogen also. 

It is the gluten of the flour that gives firmness to bread. If 
it were composed of starch alone, the bread would crumble very 
easily. It is for this reason that rice griddle - cakes break so 
readily when there is not enough flour mingled with the ricc/ 
The gluten of the flour is needed to hold together the starchy 
rice. 

There is another substance in the flour that contains nitro- 
gen. It is called albumen^ from the Latin word albus^ white. 



154 GLrXEN AND THE FOOD OF ANIMALS. 

Casein. Nitrogenous and carbonaceous substances. 

It is like the white of egg^ and is really about the same thing. 
There is nmch less albnmen in flour than of gluten. 

In the grain of wheat, then, we have three substances — starch, 
gluten, and albumen. There is much more starch than gluten, 
and the albumen is very small in amount. 

There is another substance containing nitrogen, found in 
many vegetables. We call it casein. It is nearly the same 
thing as the cheese which is contained in all milk, and which 
makes the curd. There is a great deal of this substance in veg- 
etables that grow in pods, as pease, beans, etc. 

The three substances in vegetables that furnish animals with 
nitrogen are, then, gluten, albumen, and casein. They are 
called nitrogenous substances. The most abundant is gluten, 
which occurs especially in the grains used so extensively for 
food — wheat, rye, buckwheat, barley, oats, Indian corn, etc. 

Starch and sugar have no nitrogen in them, and carbon is 
their most important element. They are said, therefore, to be 
carbonaceous substances, in distinction from the nitrogenous. 
1^0 w, these substances alone can not support life for any length 
of time. Some dogs which, by way of experiment, were fed 
upon nothing but starch and sugar, languished and died. It 
was for want of nitrogen. 

There is another class of substances, found both in vegetables 
and animals, which are carbonaceous, and have no nitrogen in 
them. They are the oils and fats. 

It is the nitrogenous substances in our food that build up and 
repair the body. Of what use, then, are starch, sugar, and the 
fats ? Their use is chiefly, if not wholly, to keep up the heat of 



GLUTEN AND THE FOOD OF ANEVIALS. 155 

Importance of gluten as nutriment. Food of the laboring man. 

the body. They are a part of the fuel, which is burning up ev- 
erywhere with the oxygen that is in the blood. 

The capacity of an article of food to nourish the body or pro- 
mote its growth is supposed to depend on the amount of nitro- 
gen there is in it. Eice is not very nutritious, because it con- 
tains a great deal of starch and very little gluten. The common 
grains, as wheat, rye, etc., are among the most nutritious vegeta- 
ble substances, for they contain much gluten. There is a great 
deal in the coverings of the grains, which, broken up, make the 
bran. Therefore bread made from bolted flour is not so nutri- 
tious as that made from unbolted flour. Pease and beans are 
very nutritious, because they contain so much of that nitrog- 
enous substance, casein, or vegetable cheese. The cabbage is 
one of the most nutritious of vegetables, for it has even more 
gluten in it than the grains. 

There is some gluten in leaves and grass, but not so much as 
in the grains. The horse, therefore, though he may thrive upon 
hay alone when idle, must have some kind of grain when he is 
worked. The wear and tear of the muscles in working makes 
a good supply of nitrogenous food necessary for repair. 

For the same reason, the food of a laboring man should be 
richer in gluten than that of a man who lives at his ease. In 
the repairing that his muscles require after the wear and tear of 
labor, it will not do to supply food that is composed only of car- 
bon, and oxygen, and hydrogen ; there must be a good quantity 
of nitrogen. If the laborer, therefore, should live chiefly on 
rice, as in China, or on potatoes, as is often the case in Ireland, 
the machinery of his body would not be well repaired, and he 



156 GLUTEN AKD THE FOOD OF ANIMALS. 

Bread the ' ' staff of life. " 

would become weak. He must have such food as bread and 
meat, with his potatoes, rice, etc., in order to get enough nitro- 
gen for growth and repair. 

Bread is called the " staff of life." Still better is it when we 
add to it the fatty carbonaceous substance, butter. Milk is such 
a combination of nitrogenous and carbonaceous substances that 
it is a complete food by itself, as is shown by the fact that chil- 
dren often live a long time on this article alone. 

Vegetable substances contain nitrogen for the very purpose 
of supplying it to animals. Animals must have it in their struct- 
ures — in their muscles, nerves, bones, skin, brain, etc. But veg- 
etables do not need it in their structures. Wood does very well 
without it, though bone and muscle can not. Since, then, veg- 
etables do not need it in their structures. Providence does not 
put it there, but makes it go into grains and other parts of veg- 
etables where animals can readily get at it, and use it in their 
food. 

Questions. — Of what are most vegetable substances composed ? Animal substances ? 
What is said of the odor of animal substances in burning ? What is said of nitrogen 
in the food of animals ? What about gluten ? What about gluten in bread ? What 
about rice cakes? What of albumen? WTiat of the three substances in wheat? 
What is said of casein ? What are nitrogenous vegetable substances ? Which is the 
most abundant of them ? What are carbonaceous vegetable substances ? What is 
said of their power to support life ? Of what special use are starch, sugar, and the 
fats ? Upon what does the nourishing power of substances depend ? What is said 
of the grains in this respect ? What of unbolted flour ? What of pease and beans ? 
What is said of animals being able to live on grass ? What of the necessity of nitrog- 
enous food for the laborer ? What about having the two kinds of food mingled ? 
What is said of bread ? Of milk ? About nitrogen in animals and vegetables ? 



FERMENTATION. VINEGAR. 157 

The change produced in fermentation. 



CHAPTEE XXVII. 

FERMENTATION. VINEGAR. 

You have heard the word ferment often used, but have you 
ever thought exactly what it means ? "When cider is first made, 
it is the mere juice of the apples. It is not fermented. It 
works, or ferments, afterward. So, also, wine is the fermented 
juice of grapes. 

What is done by the fermentation ? What is the change that 
is produced ? It is a change in the proportions of carbon, oxy- 
gen, and hydrogen, of which the substances that ferment are 
composed ; or, rather, it is a change in one of these substances. 
The substance which is changed is sugar. All those liquids 
which form intoxicating drinks by fermentation are composed 
chiefly of sugar dissolved in water, a flavor being given to the 
sirup by the plant from which it comes. Thus, the change pro- 
duced in the juice of apples is only in the sugar. The water in 
which the sugar is dissolved is not changed at all. So, also, 
grape-juice is sugar dissolved in water, with a flavor peculiar to 
the grape, and it is the sugar only that is changed in the fer- 
mentation. 

Notice now what the change produced in the sugar is. The 
sugar, so sweet to the taste, is changed into a substance called 
alcohol. It is so fiery that it must be diluted before it can be 
drunk. The strongest brandy is more than half water. 



158 FERMENTATION. VINEGAR. 

How alcohol differs from sugar in composition. 

When sugar is transformed into alcohol by fermentation, a 
change of the proportions of the carbon, oxygen, and hydrogen 
takes place, but nothing is added. On the contrary, some of the 
carbon and some of the oxygen of the sugar leave it, forming 
by their union carbonic acid gas, which flies off into the air. 
Thus, fermentation produces from the sugar two things — alco- 
hol and carbonic acid. 

This change in the sugar is caused by yeast. But how ? Does 
the yeast unite with any thing in the sugar to form the alcohol, 
as oxygen unites with iron to form rust ? 'No ; it simply forces 
the sugar to separate into two things, carbonic acid and alcohol. 
It is merely the instrument by which the sugar is split into two 
parts, and is itself unchanged. 

The working of the juice of the grape, or of cider, is caused 
by the gluten in them, which acts much like yeast. Either one 
of the nitrogenous substances, gluten, albumen, or casein, may 
act as a ferment. 

The fermentation of bread is really the same thing as the fer- 
mentation which makes drinks intoxicating. The yeast turns 
the sugar in the dough into alcohol and carbonic acid, and these 
two together puff up the bread in their efforts to escape. The 
alcohol flies off in vapor in the oven, and escapes into the air. 

In uncorking bottles of beer and cider there is a great escape 
of gas, making a lively foam. This gas is carbonic acid. It is 
made in the bottle by fermentation, and, so long as the liquid is 
confined by a tight cork, the gas is imprisoned there among the 
particles of the liquid ; but, the moment the cork is loosened, the 
gas escapes. 



FEEMEXTATIOX. VINEGAR. 159 

Beer and bottled cider. Making alcohol from barley, rye, etc. 

The production of alcohol from the grains, barlej, rye, etc., 
and from potatoes, is different from its production from apple- 
juice and grape-juice. In the grains there is a great deal of 
starch and but little sugar, and this starch must be first changed 
into sugar before alcohol can be produced. Thus, in making 
beer from barley, the first thing is to make into sugar as much 
as we can of the starch in the barley. It is done in this way : 
The grain is moistened and left in heaps; it sprouts, and, in 
doing this, much of the starch is turned into sugar, so that the 
barley has a very sweet taste. The malt^ for so this sugared 
barley is called, is now dried, and, after being bruised, is put 
into the boiler with water ; after boiling sufliciently, the liquor 
is drawn off into vats. It is now a sugary solution, and, the 
yeast being added to it, produces the alcohol from the sugar by 
fermenting. "When the mixture is boiling, hops are put in to 
give the beer a bitter fiavor, and to prevent its becoming sour. 

When cider stands in a barrel having the bung-hole open, it 
gradually turns to vinegar, undergoing another kind of fermen- 
tation. Vinegar is a mixture of water and a substance called 
acetic acid, together with small quantities of sugar, gum, and 
coloring matters. It is the alcohol in the cider which is con- 
verted into acetic acid, and the latter gives the vinegar its sour 
taste. The alcohol will not change of itself into vinegar ; there 
must be a ferment or yeast to produce this fermentation as well 
as that which forms alcohol. In making vinegar from cider in 
the common way, the work is done by the same gluten that was 
in the apple-juice and turned it into cider. 

Sometimes vinegar is manufactured in a rapid manner. It 



160 



FEEMENTATION. YINEGAR. 



A quick way of making vinegar. 




Fig- 48. ig done in barrels, as shown in 

Fig. 48. The barrel is represent- 
ed in the fignre as partly open, 
that yon may understand the ar- 
rangement. A mixture of alco- 
hol and water, having a little 
yeast in it, is allowed to drip 
through small holes in the shelf 
in the upper part of the barrel. 
The barrel is filled with loose 
shavings, and air is admitted 
through holes. The oxygen of 
the air unites with the alcohol as it trickles down through the 
shavings, and turns it into vinegar. The object of the loose 
shavings is to spread out, as we may say, the alcohol, so that 
the air can come freely to every particle of it. 

The amount of acetic acid in vinegar is very small ; a hundred 
gallons of vinegar contain only from two to five gallons of the 
acid. 

Qfiestions. — What is said about cider and wine ? What kind of change is produced 
by fermentation ? What substance in the fermenting liquids is changed ? What 
kind of a substance is formed from it ? What two things are produced in the change, 
and how ? In what way does yeast change it ? How is the change produced without 
yeast in making cider and wine ? What takes place in the fermentation of bread ? 
Explain the effervescence of bottled cider, beer, etc., when the cork is drawn. In 
making alcoholic drinks from barley, rye, etc., what change must first be produced ? 
Explain the making of malt. How is the alcoholic liquid made from this ? What is. 
vinegar made up of ? What is done to the alcohol to change it to acetic acid ? What 
effects the change in the vinegar fermentation? Describe and explain the quick 
mode of making vinegar. How much acetic acid is there in vinegar ? 



VEGETATION. 161 



Difference between a plant and a crystal in their growth. 



CHAPTEE XXVIII. 

VEGETATION. 

Every plant comes from a seed. When tlie seed is put into 
the ground, a root shoots downward into the earth, and a stalk 
shoots upward into the air. 

Observe how the root and the stalk are made. They are not 
made as crystals are. Particles are not laid on, layer after layer, 
as in the growth of a crystal. There is no life in a crystal, but 
there is in a seed. It is this life that forms the plant, and it 
has its own way of doing it. As it builds the stalk and root, it 
forms channels, or tubes, as it works along; but there are no 
such tubes in a crystal. 

Through these tubes the sap goes everywhere in the plant. 
This is true of every plant, from the smallest to the largest. 
Look at some very large and high tree. The life in a little seed 
gave it birth. It pushed up the stalk a little higher and higher, 
making tubes in it all the while ; and now that it reaches up so 
high, the sap goes up from the roots, in these tubes, out to the 
very ends of its myriad of leaves. 

Let us see now of what the seed from which all this comes is 
composed. It is mostly starch and gluten. But both of these 
substances are insoluble. Of what use^ then, can they be in 
growth, when they can not be carried up in the sap that circu- 
lates in the tubes ? Unless they can be rendered soluble, they 

L 



162 VEGETATION. 



The growth of plants. Substances found in plants. 

can be of no use — they must remain just there in the seed. As 
the seed becomes moist, a chemical change takes place ; the glu- 
ten is made soluble, and the starch is changed into sugar. So, as 
fast as the channels are made in the upshooting plant, the saj), 
with gluten and sugar dissolved in it, mounts up in them. 

All this is merely to start the growth of the plant. When 
the little root is formed, and the stalk reaches the air and puts 
out leaves, the seed has done its work. Its gluten and starch 
are used up, and the plant now gathers all its materials for 
growth from the soil and the air. It must have carbon, oxy- 
gen, hydrogen, and some nitrogen. It obtains from the air a 
large part of its carbon, taking it in at every pore in its leaves. 
Its oxygen and hydrogen it gets mostly from the water that 
comes into the mouths of the roots. The plant gets its nitro- 
gen from the ground, which contains several substances that 
supply it. One is ammonia, which, as you learned on page 
77, is composed of nitrogen and hydrogen. There is a great 
deal of this substance in some fertilizers. 

The frame-work or structure of the plant is composed almost 
entirely of carbon, oxygen, and hydrogen, while the nitrogen 
occurs chiefly in the seed or grain, where it is deposited for the 
use of man and other animals. Besides these four substances, 
some others are found in vegetables, but in a much smaller 
amount. Silica has been mentioned as occurring in stalks of 
grain ; sulphur occurs in mustard and in the onion ; and very 
small quantities of phosphorus, iron, lime, potash, etc., are also 
found in plants. All these are carried up in the sap through 
the channels mentioned in the first part of this chapter. 



VEGETATION. 163 



Nature of sap. Result of burning wood. 

Now, think what sap is. Most of it is water, and this con- 
tains in solution the various substances above mentioned. Wa- 
ter, then, not only furnishes the plant with oxygen and hydro- 
gen, but it is the means by which the other substances needed 
by the plant are carried about in its channels or tubes to the 
very ends of the leaves. Some of the water remains in the 
plant, giving its oxygen and hydrogen to it to help form wood, 
starch, gluten, sugar, etc. ; but most of it is breathed out into 
the air through the little pores in the leaves. 

Juicy fruits contain a great deal of water : the water-melon, 
you know, seems to be nearly all water, with a little sugar dis- 
solved in it. When wood is just cut, it is said to be green ; that 
is, it is full of sap. This prevents its burning well ; but if it be 
exposed to the air, this water passes off, and the wood becomes 
dry. 

When wood is burned in such a way that there is an abun- 
dant supply of oxygen, nothing but ashes remains. These have 
but little bulk compared with the wood. Only one or two 
pounds of ashes are obtained from a hundred pounds of wood. 
What has become of the remainder, the ninety-eight pounds of 
wood? It has gone off into the air. As a large part of the 
wood comes from the air, so most of it, in burning, returns to 
the air. Much of what passes off is water, for even what we 
call dry wood contains considerable water. This passes off as 
vapor. Then most of the carbon of the wood, uniting with oxy- 
gen, flies off as carbonic acid. Some of the oxygen of the wood 
is disposed of in this way, and some of it unites with the hy- 
drogen of the wood to form water, which goes off as vapor. If 



164 VEGETATION. 



Composition of wood ashes. Living beauty from decay and death. 

this were all, the smoke would not be visible, for yon can not 
see either vapor or carbonic acid gas; bnt some of the carbon 
goes np in little particles, and these make the smoke. 

What is really the composition of ashes ? They are composed 
of potash, silica, lime, iron-rust, etc. These snbstances are f onnd 
in different proportions in the ashes of different plants. Thns 
there is more silica in the ashes of straw than in those of com- 
mon wood. There is much potash in the ashes of wood, and for 
this reason they are nsed for obtaining that substance for mak- 
ing soap, as noticed on page 109. 

Let ns look a little more at what plants get from the ground 
to make them grow, and how they do it. They get all the dif- 
ferent ingredients, except carbon, from this source. Most of this 
they get from the air, but some of it comes from the ground. 
They get, then, from the ground all their oxygen, hydrogen, and 
nitrogen, and part of their carbon, and, besides these, small 
quantities of the various other things which they need — as pot- 
ash, lime, iYon, sulphur, phosphorus, etc. 

Now, much of all these ingredients comes from the decay of 
plants. Every year great quantities of dead leaves and other 
parts of plants become a part of the earth, and help to form the 
plants of another year. 

It is thus that decay and death furnish material for new life. 
The living beauty that feasts our eyes in -the spring comes, to a 
great extent, from what fell to the ground and died the previous 
year ; and not only so, but tha4: which in its putrefaction offends 
our sense of smell, becomes a part of the plants which, with their 
leaves and flowers, so delight our eyes, and of the fruits which 



VEGETATION. 165 



Composition of vegetable oils. Acids in plants. 

are so pleasant to our taste. The nitrogen, wliich is one of the 
ingredients of the ammonia which smells so strongly in the ma- 
nure of the stable, goes up the channels of the wheat-stalk, and 
helps to make the gluten of the grain, and as you eat it in the 
bread it helps to form the substance of your body. 

Some substances are composed of only two of the chief ingre- 
dients of plants, carbon and hydrogen. To this class belong the 
oils of orange-peel, lemon, and pepper. The oil of turpentine 
is also one, as well as caoutchouc, or India rubber. 

Other oils are composed of three of the four grand ingredi- 
ents of plants, viz., carbon, oxygen, and hydrogen. Among 
these are the oils of peppermint, valerian, anise, orange-flowers, 
rose -petals, etc. Camphor, also, is composed of these three in- 
gredients. 

Some oils have considerable sulphur in them, as oil of mus- 
tard, onion, asafetida, etc. You know that a spoon, if left in 
mustard, becomes dark colored. This is because the sulphur in 
the mustard unites with the silver to form a sulphide of silver. 

There are various acids in plants ; these are composed of car- 
bon, oxygen, and hydrogen in different proportions. Tartaric 
acid, for example, is the peculiar acid of grapes ; malic acid oc- 
curs in apples, pears, and some other fruits ; oxalic acid in sor- 
rel ; citric acid in lemons, oranges, currants, etc. These various 
acids are combined with potash, soda, lime, and other bases ; tar- 
taric acid, in the juice of the grape, is combined with potash, 
forming a salt called cream of tartar; this substance collects 
upon the inside of wine casks, depositing from the wine. 

There are many different coloring substances in vegetables, as 



16(5 VEGETATION.' 



Coloring matters. Alkalx)icls. 

indigo, the coloring matter of logwood, of madder -root, etc. 
They are composed, like the acids, of carbon, oxygen, and hy- 
drogen, or of these with nitrogen. 

Another and interesting class of substances occurring in 
plants must yet be mentioned ; we refer to the so-called alka- 
loids — quinine, morphine, and the like. Quinine, together with 
a number of similar bodies, is obtained from the bark of the 
cinchona^ a tree cultivated chiefly in South America: it is a 
very useful medicine. Morphine comes from opium, theine 
from tea and coffee, strychnine from nux vomica, nicotine from 
tobacco. The two substances last named are among the most 
deadly poisons known : less than a drop of nicotine placed on 
the tongue causes instant death. 

Questions. — What takes place when a seed is put into the ground ? How are the 
root and stalk made differently from crystals ? What is said about the sap in plants ? 
What is said about a large tree ? Of what substances is a seed composed ? What 
change is needed in these, and how is it effected ? What becomes of the seed ? Aft- 
er the seed is gone, from what is the plant nourished ? What materials of growth 
must it have ? How does it get its carbon ? How its oxygen and hydrogen ? How 
its nitrogen ? Of what elements are the structures in plants made ? Where in plants 
is nitrogen deposited, and for what purpose ? Mention some other substances that 
are in some plants. What is sap ? What is said of the uses of the water in sap ? 
When wood is burned, how much of it becomes ashes ? What becomes of the rest ? 
Why is smoke visible ? What substances are in ashes ? What do plants get from 
the ground ? What is said of decay as furnishing materials for growth ? What is 
said of putrefying substances ? Mention some substances composed of carbon and 
hydrogen only. What oils are composed of three of the grand elements? What 
oils have considerable sulphur in them ? What is said of vegetable acids ? What of 
coloring substances ? From what is quinine obtained ? From what morphine, theine, 
strychnine, and nicotine ? 



HOW FOOD MAKES ANIMALS GEOW. ' 167 

Amount of water in the blood. Other ingredients of the blood. 



CHAPTEK XXIX. 

HOW FOOD MAKES ANIIVIALS GEOW. 

The blood is to an animal what the sap is to a vegetable. The 
sap is water, containing in solution whatever is necessary to the 
growth or building-up of the plant ; and so the blood is water, 
containing in solution whatever is necessary to the growth and 
nutriment of the animal. 

About four-fifths of our blood is water ; that is, in every five 
pounds of blood there are four of water. You will, of course, 
want to know what substances are dissolved in this ; that is, what 
make up the other fifth of the blood. They are carbon, oxygen, 
hydrogen, nitrogen, chlorine, sodium, potassium, calcium, mag- 
nesium, iron, phosphorus, and sulphur. 

These substances, you remember, are elements, not compounds. 
But they do not appear as elements in the blood. They are 
combined in various ways. For example, the iron is united 
with some of the oxygen, forming oxide of iron, and some of 
this oxide is united with phosphoric acid, making phosphate of 
iron. So most of the chlorine is united with the metal sodium, 
forming common salt. About one -third of that part of the 
blood which is not water is albumen. This closely resembles 
the albumen of many vegetables, and is likewise composed of the 
four grand elements, carbon, oxygen, hydrogen, and nitrogen. 



168 now FOOD MAKES ANIMALS GROW. 

How different substances get into the blood. Chemistry of the stomach. 

How do all these different substances get into the blood? 
They come from the food we eat. All that part of the food 
which will serve to nourish the body is absorbed by the stom- 
ach, and is put into the blood and becomes a part of it. It is 
exactly as the little mouths in the roots of a plant suck up from 
the earth what is proper to go into the sap. The fact that the 
root of a plant and the stomach of an animal thus perform sini- 
ilar duties is fully illustrated in Chapter TV. of the Second Part 
of the Child's Book of JSTature. 

But all the substances in our blood are not always in our food. 
How is it, then, that the blood is always supplied with them ? 
It is because the food contains the material of which these sub- 
stances are made. Chemical operations go on in the stomach ; 
it is a sort of chemical laboratory. For instance, you eat, in one 
way and another, considerable sugar; but there is no sugar in 
the blood. How is this ? Is all this sugar lost ? No ; it is all 
used, but it does not go into the blood as sugar ; it helps to make 
some other things that enter the blood. 

All substances which enter the stomach are not completely 
decomposed, however ; salt is one of these : it forms part of our 
food and is contained in our blood. 

Oxygen, the lung-food mentioned on page 15, does not enter 
the blood from the food solely ; indeed, a large part of it goes in 
by the lungs when we breathe. 

All the different parts of the body, as we told you in Chapters 
I. and II. of the Second Part of the Child's Book of ITature, are 
made from the blood. For this purpose the blood, containing 
all the different substances mentioned, goes or circulates through- 



now FOOD MAKES ANIIVIALS GEOW. 1G9 

How the body is bailt. The composition of bones. 

out the body; and the materials needed for building are used 
just where they are wanted. For example, where it is necessary 
to make bone, the materials for bone are taken from the blood, 
and are arranged so as to make the bone of the right shape. 
Phosphate of lime, one of these materials, is in the blood, all 
ready for use. 

You learned on page 95 that the bones of animals are made 
chiefly of phosphate of lime, a salt containing the three ingre- 
dients, phosphorus, calcium, and oxygen. 

This bone material enters the body through the food eaten, 
and so gets into the blood, and goes to the bones, where it is 
needed to make them grow. A certain amount of phosphate of 
lime occurs in both animal and vegetable food ; a small quantity 
also is found in milk. 

You see, then, that it is with the phosphate of lime in our 
bones as it is with the carbonate of lime in the shells of oysters 
and other shell-fish, in the stony skeletons of coral animals, and 
in the egg-shells of birds. The building material is swallowed, 
and, going into the blood, is carried in it to where it is wanted 
for building. 

Think, now, whence came all of the carbonate and phosphate 
of lime contained in the bones and shells of animals. They 
came from the rocks. But how did these substances get from 
the rocks into your bones ? A great deal of breaking-up, grind- 
ing, etc., was necessary for this. The rocks are crumbling and 
falling to pieces all the time, from the influence of frost and 
water and air. Then the soft, broken material mixes with the 
earth, and becomes very finely divided. Particles of it, there- 



170 HOW FOOD MAKES ANIMALS GEOW. 

Whence phosphate of lime is obtained. Iron in the blood. 

fore, continually get into plants in the sap which the roots suck 
up. If you eat vegetables, then, or the meat of an animal that 
has eaten vegetables, you introduce into your stomach, and so 
into your blood, some of the phosphate of lime derived from the 
rocks. 

In like manner, where nerve is to be made, those materials 
are taken from the blood of which nerve is composed ; and the 
same is true of all other parts of the body. Once in a while 
nature makes a mistake in this matter. For instance, bony sub- 
stance is formed in some part where it is not wanted, as in the 
arteries or in the heart. This causes disease. But, generally, 
every thing is put in the right place. 

Brain and nerve are composed of a variety of substances — 
fatty substances, albumen, phosphorus, sulphur, potash, lime, 
magnesia, etc. Phosphorus is an essential ingredient of the 
brain ; that is, the brain can not do without it. We have heard 
students recommended to eat freely of eggs, because they con- 
tain considerable phosphorus. We do not believe, however, that 
this would make a dull scholar bright. Something else besides 
phosphorus is needed for that. 

Hair, feathers, bone, and nails contain sulphur and silica, 
combined with the other ingredients. 

There is iron in the blood. It is in the substance that gives 
the red color to this fluid. There is also a very little of it in the 
hair, helping, with the silica, to give it strength. Exactly of 
what use it is in the blood we do not know. When persons 
are pale and weak they have not enough of it in the blood, 
and they should take medicines containing iron. 



HOW FOOD MAKES ANIMALS GKOW. lYl 

Milk a very complex food. 

You havQ learned what a variety of substances occur in the 
blood. Now,, when one eats a variety of food, it is easy to see 
how all these various substances are furnished to the blood. 
But how is it with a child that lives only upon milk ? Can 
there be mingled together in that white fluid all the substances 
mentioned ? If they were not, there would be something miss- 
ing in the building-up of the body. If, for example, there were 
no phosphate of lime in milk, the bones of the infant living on 
milk would grow, but they would be soft, and would bend very 
easily, since it is the phosphate of lime that makes them hard 
and rigid. Milk contains this, and all the other substances re- 
quired for the growth of the body. It contains all the nutri- 
tious substances which can be gathered from both meats and 
vegetables. 

Questions. — Give the comparison between sap and blood. How much of the blood 
is water ? What elements are in the blood ? Mention some of the combinations of 
these in the blood. What is said of the albumen in the blood ? How does the blood 
get all the substances that are in it ? Give the comparison between the stomach of 
the animal and the root of the plant. How is it that there are some substances in 
the blood that are not in the food ? What is said of the sugar that we eat ? What 
of salt ? What is said of the circulation of the materials for building different parts 
of the body ? What of making bone ? Of what are bones composed ? Whence 
come the Hme - salts contained in bones ? What are the substances in brain and 
nerves ? W^hat is said of eating eggs ? In what animal structures does sulphur oc- 
cur ? What is said of iron in the blood ? What is said of milk ? 



17^ CONCLUDING OBSEEYATIONS. 

Comparative abundance of the elements. 



CHAPTEE XXX. 

COiSrCLUDING OBSEKYATIONS. 

You have learned in this little book that the whole world is 
bnilt up chiefly of a few elements. In fact, there are but sixty- 
three elements, and of these about fifty are metals. Most of 
these exist in small quantities. A few of them are very abun- 
' dant, as iron, calcium, sodium, aluminium, copper, lead, etc. But 
the most abundant substances in the world are not metals. They 
are oxygen, carbon, nitrogen, hydrogen, silicon, sulphur, chlorine, 
etc. Nearly, if not quite, one half of the world is a gas — oxy- 
gen. And the four grand elements used in the making -up of 
the earth are oxygen, carbon, hydrogen, and nitrogen. Three 
of these are gases. Water, the liquid present in almost every 
thing, is composed of two of them. All living substances, veg- 
etable and animal, are essentially composed either of three of 
them or of the whole four. 

Although the number of the chemical elements is thus lim- 
ited, the variety of the substances formed by their combinations 
is immense : this variety is increased by the fact that two or 
more elements may combine in several proportions, as, for ex- 
ample, oxygen and nitrogen, which form five compounds, dif- 
fering widely in their characters. In living organisms we have 
most wonderful examples of the Creator's power in producing 
an enormous variety of substances from a very few materials. 



CONCLUDING- OBSERVATIONS. 173 

Some of the combinations of oxygen noticed. Its activity as an agent. 

In the latter case, the variation in form and properties is be- 
lieved to be owing to variation in the arrangement of the parti- 
cles of which the substances are composed. 

Oxygen combines with all the elements but one. With many 
of them it unites very readily, with some eagerly; but with oth- 
ers, as gold, platinum, etc., it unites only when forced to do so, 
and when it is combined with them it is easy to cause them to 
part company. 

Let us recall a few of the combinations which oxygen forms. 
With hydrogen it forms the most abundant of all compounds, 
water. Mixed with nitrogen and carbonic acid gas, it forms the 
most abundant of all mixtures, the atmosphere. It forms, with' 
the metals, oxides, a very numerous class of substances. By com- 
bining with nitrogen, sulphur, phosphorus, chlorine, silicon, etc., 
and the elements of water, it forms acids. One of these oxides, 
silica, is one of the most plentiful hard substances in the earth, 
being in the granite and many other rocks, and constituting, 
for the most part, all the sand of the land and sea, and a large 
portion even of the fertile earth. Then we have oxygen in all 
the potash and lime, and in their carbonates ; the carbonates of 
lime in the forms of limestone and chalk and marble being 
very abundant substances, sometimes even forming mountains. 
Besides all this, oxygen is one of the chief ingredients in vege- 
table and animal substances. 

But you see the importance of this element not only in its 
abundance, but also in its active agencies. It is no laggard in 
the chemical movements which are everywhere going on ; it is 
a lively, busy agent. It is the grand supporter of combustion. 



174 CONCLUDING- OBSERVATIONS. 

Changes in the forms of matter. 

keeping every fire and liglit burning. It maintains the life of 
all animals by entering the lungs continually, and it conveys 
away carbon from their -bodies to the leaves of plants by uniting 
with it to form carbonic acid. It rusts the metals wherever it 
can get hold of them, and it has such an affiuity for some of 
them that they can never be found except in union with oxy- 
gen. 

The changes in the forms of matter from solid to gaseous or 
liquid, and the reverse — changes in which oxygen commonly is 
so busy — are very wonderful when we look into them. Thus, in 
the burning of wood, the oxygen of the air unites with the car- 
bon and hydrogen of the solid wood, forming the gas carbonic 
acid, and water, which flies off with the gas in vapor. From one 
hundred pounds of wood, as already stated on page 163, we usu- 
ally obtain but about two pounds of ashes. The ninety-eight 
pounds, which are water and carbonic acid, have flown off into 
the air. What becomes of them? Let us trace their move- 
ments. The water gathers in the clouds to fall to the earth, or 
settles upon the ground in the form of dew. In whatever way 
it comes to the earth, it there goes to work again, and works 
chemically, for some of it flnds its way into the roots of plants, 
and helps to form their substance by combining with carbon 
and nitrogen. That part of the ninety - eight pounds which is 
carbonic -acid floats off to be absorbed by leaves, in order to 
furnish carbon, by chemical operations, to the plants and trees. 
The oxygen that has thus conveyed, as we may say, the carbon 
to the leaves, returns again, in the air, to the lungs of animals ; 
and some of the carbon thus furnished to plants comes back also 



CONCLUDING OBSERVATIONS. 175 

Chemistry does not destroy matter, but only changes it. 

to animals in the food which they eat, to repeat its chemical 
work in them. 

This leads us to remark that much of the matter in the world 
is constantly circulating back and forth between animals and 
vegetables and the earth, and in this circulation it is all the 
time changing. The grand means by which this circulation is 
carried on are air and water. These are everywhere in motion, 
and they carry with them a great many substances wherever 
they go. For example, the air takes the carbon from our lungs, 
and carries it aloft for the leaves to take in, and brings back to 
our lungs the oxygen that the leaves breathe out. As an exam- 
ple of the agency of water in this circulation, you have seen 
how it dissolves the carbonate of lime from the rocks and the 
earth (Chapter XYIII.), and carries it into the sea for the shell 
animals to use in the construction of their shells. So, also, wa- 
ter brings the silica to the grasses and grains, that it may be 
sucked up by their roots. In these and many other ways, air 
and water are ever busy distributing substances, solid as well as 
liquid and gaseous, in every direction ; and they thus have more 
influence than any other agents in carrying on the grand chem- 
ical operations of the world. They are not only continually 
changing themselves, but they produce changes in other sub- 
stances by bringing them together so that they can act upon 
each other. 

The world is emphatically a world of change; and in the 
changes that take place there is no loss, no destruction of mate- 
rial. When any thing burns up, as we express it, there is no 
destruction of any substance ; there is merely chauge from one 



176 CONCLUDLNG OBSEEYATIONS. 

Chemical force at work everywhere. 

form to another, and what seems to vanish in air soon re-appears 
in the solid forms growing up all around us. So, when decay 
takes place, there is no loss of a single particle of matter, but 
chemical force is simply bringing about new combinations and 
arrangements of the particles of the decaying substance. Chem- 
ical force is at work throughout the universe, not destroying, but 
pulling to pieces only to rebuild again, and in all its manifold 
operations reflecting the wisdom, love, and power of an Omnip- 
otent Being. 

Questions. — How many elements are there ? How many of them are metals ? 
Name some of the most abundant of them. What are the most abundant of all the 
elements ? What are the four chief elements ? Which of them is the most abun- 
dant ? What is said of the variety of the substances formed by the combination of 
the elements ? Give what is said of some of the combinations of oxygen. What is 
said of its activity as an agent ? State what is said of the changes that take place 
in the combustion of wood and in consequence of it. What is said of the circulation 
of matter ? What is said of the changes that chemistry is effecting in the world ? 



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